S-NAIL(1)

📦 version 14.9.22, in centos-stream 9

💅 S-NAIL(1) — General Commands Manual 💅

🎀 NAME 🎀

S-nail [v14.9.22] — send and receive Internet mail ✨

🌈 SYNOPSIS 🌈

s-nail [-DdEFinv~#] [-: spec] [-A account] [:-a attachment:]
       [:-b bcc-addr:] [:-C "field: body":] [:-c cc-addr:]
       [-M type | -m file | -q file | -t] [-r from-addr]
       [:-S var[=value]:] [-s subject] [:-T "field: addr":] [:-X cmd:]
       [:-Y cmd:] [-.] :to-addr: [-- :mta-option:]

s-nail [-DdEeHiNnRv~#] [-: spec] [-A account] [:-C "field: body":]
       [-L spec] [-r from-addr] [:-S var[=value]:] [-u user] [:-X cmd:]
       [:-Y cmd:] [-- :mta-option:]
s-nail [-DdEeHiNnRv~#] [-: spec] [-A account] [:-C "field: body":] -f
       [-L spec] [-r from-addr] [:-S var[=value]:] [:-X cmd:] [:-Y cmd:]
       [file] [-- :mta-option:]

s-nail -h | --help
s-nail -V | --version

🦋 DESCRIPTION 🦋

🚨 Note: S-nail (S-nail) will see major changes in v15.0 (circa 2022). Some backward incompatibilities cannot be avoided. “COMMANDS” change to “Shell-style argument quoting”, and shell metacharacters will become (more) meaningful. Some commands accept new syntax today via wysh (“Command modifiers”). Behaviour is flagged [v15-compat] and [no v15-compat], setting v15-compat (“INTERNAL VARIABLES”) will choose new behaviour when applicable; giving it a value makes wysh an implied default. [Obsolete] flags what will vanish. ⚠️ Warning! v15-compat (with value) will be a default in v14.10.0!

S-nail is literally your simple, friendly little home base for sending and receiving mail. It’s meant to give you the functionality of the POSIX mailx(1) command, but it’s MIME capable and can optionally offer extensions for line editing, S/MIME, SMTP, POP3, and more. It splits incoming mail into its constituent messages and lets you deal with them in any order you want. It gives you many “COMMANDS” and “INTERNAL VARIABLES” for manipulating messages and sending mail. It also hands you simple editing capabilities so composing outgoing messages is easier, plus increasingly powerful and reliable non-interactive scripting capabilities. 💖

🌸 Options 🌸

-: spec, --resource-files=.. — controls loading of “Resource files” (as via source): spec is parsed case-insensitively; the letter s means the system wide s-nail.rc, and u means the user's personal file ~/.mailrc. The original system wide resource is also compiled-in and reachable via x. The letters - and / disable usage of resource files. Order matters, and the default is su. This option overrides -n.
-A name, --account=.. — activates user account name after program startup is complete (resource files loaded, only -X commands are to be executed), and switches to its “primary system mailbox” (most likely the inbox). If activation fails, the program exits if used non-interactively, or if any of errexit or posix are set.
-a file[=input-charset[#output-charset]], --attach=.. — (Send mode) attach file. For Compose mode opportunities, refer to ~@ and ~^. file is subject to tilde expansion (see “Filename transformations” and folder); if it is not accessible but contains a = character, anything before the last = will be used as the filename, and anything thereafter as a character set specification, as shown. If only an input character set is specified, the input side is fixed and no character set conversion will be applied; an empty string or the special string hyphen-minus - is taken for ttycharset (the default). If an output character set has also been specified, the desired conversion is performed immediately, not considering file type and content, except for an empty string or hyphen-minus -, which select the default conversion algorithm (see “Character sets”): no immediate conversion is performed, and file and its contents will be MIME-classified first (“HTML mail and MIME attachments, The mime.types files”) — only the latter mode is available unless features includes ,+iconv,.
-B — ([Obsolete]: S-nail will always use line-buffered output; to gain line-buffered input even in batch mode, enable batch mode via -#.)
-b addr, --bcc=.. — (Send mode) send a blind carbon copy to recipient addr. The option may be used multiple times. Also see the section “On sending mail, and non-interactive mode”.
-C "field: body", --custom-header=.. — create a custom header which persists for an entire session. A custom header consists of the field name followed by a colon : and the field content body, for example -C "Blah: Neminem laede; imo omnes, quantum potes, juva". Standard header field names cannot be overwritten by custom headers. Runtime adjustable custom headers are available via the variable customhdr, and in Compose mode ~^, one of the “COMMAND ESCAPES”, as well as digmsg are the most flexible and powerful options to manage message headers. This option may be used multiple times.
-c addr, --cc=.. — (Send mode) just like -b, except it places the argument in the list of carbon copies.
-D, --disconnected — [Option] startup with disconnected set.
-d, --debug — enter a debug-only sandbox mode by setting the internal variable debug; the same can be achieved via -S debug or set debug. Also see -v.
-E, --discard-empty-messages — (Send mode) sets skipemptybody and thus discards messages with an empty message part body, successfully.
-e, --check-and-exit — just check if mail is present (in the system inbox or the one specified via -f): if yes, return an exit status of zero; a non-zero value otherwise. To restrict the set of mails to consider in this evaluation, a message specification can be added with the option -L. Quickrun: does not open an interactive session.
-F — (Send mode) save the message to send in a file named after the local part of the first recipient's address (instead of in record).
-f, --file — read in the contents of the user's “secondary mailbox” MBOX (or the specified file) for processing; when S-nail is quit, it writes undeleted messages back to this file (but be aware of the hold option). The optional file argument will undergo some special “Filename transformations” (as via folder). Note that file is not an argument to the flag -f, but is instead taken from the command line after option processing has been completed. In order to use a file that starts with a hyphen-minus, prefix with a relative path, as in ./-hyphenbox.mbox.
-H, --header-summary — display a summary of headers for the given folder (depending on -u, inbox or MAIL, or as specified via -f), then exit. A configurable summary view is available via the option -L. This mode does not honour showlast. Quickrun: does not open an interactive session.
-h, --help — show a brief usage summary; use --long-help for a list of long options.
-i — sets ignore to ignore tty interrupt signals.
-L spec, --search=.. — display a summary of headers of all messages that match the given spec in the folder found by the same algorithm used by -H, then exit. See the section “Specifying messages” for the format of spec. This mode does not honour showlast. If the -e option has been given in addition, no header summary is produced, but S-nail will instead indicate via its exit status whether spec matched any messages (0) or not (1); note that any verbose output is suppressed in this mode and must instead be enabled explicitly (see -v). Quickrun: does not open an interactive session.
-M type — (Send mode) will flag standard input with the MIME Content-Type: set to the given known type (“HTML mail and MIME attachments, The mime.types files”) and use it as the main message body. [v15 behaviour may differ] Using this option will bypass processing of message-inject-head and message-inject-tail. Also see -q, -m, -t.
-m file — (Send mode) MIME classify the specified file and use it as the main message body. [v15 behaviour may differ] Using this option will bypass processing of message-inject-head and message-inject-tail. Also see -q, -M, -t.
-N, --no-header-summary — inhibit the initial display of message headers when reading mail or editing a mailbox folder by calling unset for the internal variable header.
-n — standard flag that inhibits reading the system wide s-nail.rc upon startup. The option -: allows more control over the startup sequence; also see “Resource files”.
-q file, --quote-file=.. — (Send mode) initialize the message body with the contents of file, which may be standard input - only in non-interactive context. Also see -M, -m, -t.
-R, --read-only — any mailbox folder aka folder opened will be in read-only mode.
-r from-addr, --from-address=.. — the RFC 5321 reverse-path used for relaying and delegating messages to its destination(s), for example to report delivery errors, is normally derived from the address which appears in the from header (or, if that contains multiple addresses, in sender). A file-based aka local executable mta (Mail-Transfer-Agent), however, instead uses the local identity of the initiating user.

okay so, still riding the -r wave here 🏄 — this next bit is all about what happens when that from-addr you handed over is a single addressee:

When this command line option is used, the given single addressee from-addr gets assigned to the internal variable from, but that's not all — the command line option -f from-addr will also be passed to a file-based mta whenever a message is sent. And if from-addr happens to include a user name? The address components get separated, and that name part gets passed to the file-based mta individually via -F name. And even though it's not a recipient, the shquote expandaddr flag is supported. 💅

If you pass an empty string as from-addr, then the content of the variable from gets evaluated and used for this purpose whenever the file-based mta is contacted — or, if that variable contains multiple addresses, sender gets used instead. By default (so, without -r), neither -f nor -F command line options are used when contacting a file-based MTA, unless you force this automatic deduction by setting the internal variable r-option-implicit.

Remarks, and listen up because this is a real one: lots of default installations and sites disallow overriding the local user identity like this unless either the MTA has been configured accordingly, or you're a member of a group with special privileges. And passing an invalid address will cause an error. No cap. 😭

-S var[=value], --set=.. — sets a variable (or, with a prefix string no, unsets it, as documented in “INTERNAL VARIABLES”) and optionally assigns value, if that's supported. [v15 behaviour may differ] The entire expression is evaluated as if it were specified within dollar-single-quotes (peep “Shell-style argument quoting”) when the internal variable v15-compat is set. If the operation fails, the program will exit if any of errexit or posix are set. Also important: settings established via -S cannot be changed from within “Resource files” or an account switch initiated by -A. They become mutable again right before commands registered via -X are executed. 🎀
-s subject, --subject=.. — (Send mode) specifies the subject of the message to be sent. Newline (NL) and carriage-return (CR) bytes are invalid and get normalized to space (SP) characters. ✨
-T "field: addr", --target=.. — (Send mode) adds addr to the list of receivers targeted by field; for now the only supported ones are bcc, cc, fcc, and to. The field and the body (address) are separated by a colon : and optionally blank (space, tabulator) characters. The shquote expandaddr flag is supported. addr gets parsed like a message header address line — as if it were part of a template message fed in via -t — and the same modifier suffix is supported. You can use this option multiple times, bestie. 💖
-t, --template — (Send mode) the text message you give (on standard input) is expected to contain one or multiple plain text message headers, separated from the message body by an empty line. [v15 behaviour may differ] Readily prepared MIME mail messages cannot be passed. 🫠 Headers can span multiple consecutive lines if the follow lines start with any amount of whitespace. A line starting with the number sign # in the first column is ignored. Message recipients can be given via the message headers To:, Cc:, Bcc: (the ?single modifier enforces treatment as a single addressee, for example To?single: exa, <m@ple>) or Fcc: — they'll be added to any recipients specified on the command line, and are likewise subject to expandaddr validity checks. And if a message subject is specified via Subject:, that one gets used in favour of one given on the command line. 👑

More optional headers are Reply-To: (possibly overriding reply-to), Sender: (sender), From: (from and / or option -r). Message-ID:, In-Reply-To:, References: and Mail-Followup-To: — by default created automatically dependent on message context — will be used if specified (a special address massage will however still occur for the latter). Any other custom header field (also see -C, customhdr and ~^) is passed through entirely unchanged, and in conjunction with the options -~ or -# it's possible to embed “COMMAND ESCAPES”. Also see -M, -m, -q. 🦋

-u user, --inbox-of=.. — initially reads the “primary system mailbox” of user, appropriate privileges presumed; effectively identical to -f %user. 🌸
-V, --version — shows S-nails version and exits. The command version will also show the list of features: $ s-nail -:/ -Xversion -Xx. 💫
-v, --verbose — sets the internal variable verbose to enable logging of informational context messages. (Increases the level of verbosity when used multiple times.) Also see -d. 🔍
-X cmd, --startup-cmd=.. — adds the given cmd (or multiple, for a multiline argument) to a list of commands to be executed before normal operation starts. The commands get evaluated as a unit, just as via source. Correlates with -# and errexit. 🌟
-Y cmd, --cmd=.. — adds the given cmd (or multiple, for a multiline argument) to a list of commands to be executed after normal operation has started. The commands get evaluated successively in the given order, and as if given on the program's standard input — before interactive prompting begins in interactive mode, after standard input has been consumed otherwise. 🎯
-~, --enable-cmd-escapes — enables “COMMAND ESCAPES” in (Compose mode) even in non-interactive use cases. This can for example be used to automatically format the composed message text before sending the message:

$ ( echo 'line    one. Word.     Word2.';\
    echo '~| /usr/bin/fmt -tuw66' ) |\
  LC_ALL=C s-nail -d~:/ -Sttycharset=utf-8 bob@exam.ple

-#, --batch-mode — enables batch mode, and omg it does a lot: standard input is made line buffered, the complete set of (interactive) commands is available, processing of “COMMAND ESCAPES” is enabled in “Compose mode”, and diverse “INTERNAL VARIABLES” get adjusted for batch necessities, exactly as if done via -S: emptystart, noerrexit, noheader, noposix, quiet, sendwait, typescript-mode as well as MAIL, MBOX and inbox (the latter three to /dev/null). Also, the values of COLUMNS and LINES are looked up, and acted upon. The following prepares an email message in a batched dry run:

$ for name in bob alice@exam.ple lisa@exam.ple; do
    printf 'mail %s\n~s ubject\nText\n~.\n' "${name}"
  done |
  LC_ALL=C s-nail -#:x -Smta=test \
    -X'alias bob bob@exam.ple'

-., --end-options — this flag forces termination of option processing in order to prevent “option injection” (attacks). 🛡️ It also forcefully puts S-nail into send mode, see “On sending mail, and non-interactive mode”.

If the setting of expandargv allows their recognition, all mta-option arguments given at the end of the command line after a -- separator will be passed through to a file-based mta (Mail-Transfer-Agent) and persist for the entire session. expandargv constraints do not apply to the content of mta-arguments. Command line receiver address handling supports the shquote constraint of expandaddr — for more, please see “On sending mail, and non-interactive mode”. 💌

$ s-nail -#:/ -X 'addrcodec enc Hey, ho <silver@go>' -Xx

🌈 A starter 🌈

S-nail is a direct descendant of BSD Mail, itself a successor to the Research Unix mail which “was there from the start” according to “HISTORY”. So basically it's the user side of the Unix mail system, while the system side (Mail-Transfer-Agent, MTA) was traditionally taken by sendmail(8) (and most MTAs provide a binary of this name for compatibility reasons). But good news: if the [Option]al SMTP mta is included in the features of S-nail, then the system side is not a mandatory precondition for mail delivery. 🎉

S-nail strives for compliance with the POSIX mailx(1) standard, but posix — one of the “INTERNAL VARIABLES” — or its “ENVIRONMENT”al equivalent POSIXLY_CORRECT needs to be set to adjust behaviour to be almost on par. Almost, because there's one important difference: POSIX “Shell-style argument quoting” is ([v15 behaviour may differ] increasingly) used instead of the “Old-style argument quoting” that the standard documents, which is believed to be a feature. 😌 The builtin as well as the (default) global s-nail.rc “Resource files” already bend the standard imposed settings a bit.

For example, hold and keepsave are set in order to suppress the automatic moving of messages to the “secondary mailbox” MBOX that would otherwise occur (see “Message states”), and keep to not remove empty system MBOX mailbox files (or all empty such files in posix mode) so we avoid mangling of file permissions when files eventually get recreated. 🙈

To enter interactive mode even if the initial mailbox is empty, emptystart is set; editheaders to allow editing of headers as well as fullnames to not strip down addresses in “Compose mode”; and quote to include the message that's being responded to when replying, which is indented by an indentprefix that also deviates from standard imposed settings. mime-counter-evidence is fully enabled too. It sets followup-to-honour and reply-to-honour to comply with reply address desires. 💅

Credentials and other settings are easily addressable by grouping them via account. The file mode creation mask can be managed with umask. Files and shell pipe output can be sourced for evaluation, also during startup from within the “Resource files”. And informational context can be available by setting verbose or debug (as via -v, -d). 🎀

✨ On sending mail, and non-interactive mode ✨

Okay so bestie, if you wanna send a message to one or more people and you’re using a local or built-in mta (that’s Mail-Transfer-Agent, the thing that actually delivers the generated mail message), S-nail can be invoked with arguments that are literally the names of the people the mail will be sent to. And the command line options -b and -c? They add (blind) carbon copy receivers. Slay.

# Via test MTA
$ echo Hello, world | s-nail -:/ -Smta=test -s test $LOGNAME

# Via sendmail(1) MTA
$ </dev/null s-nail -:x -s test $LOGNAME

# Debug dry-run mode:
$ </dev/null LC_ALL=C s-nail -d -:/ \
   -Sttycharset=utf8 -Sfullnames \
   -b bcc@exam.ple -c cc@exam.ple -. \
   '(Lovely) Bob <bob@exam.ple>' eric@exam.ple

# With SMTP (no real sending due to -d debug dry-run)
$ LC_ALL=C s-nail -d -:/ -Sv15-compat -Sttycharset=utf8 \
    -S mta=smtps://mylogin@exam.ple:465 -Ssmtp-auth=none \
    -S from=scriptreply@exam.ple \
    -a /etc/mail.rc --end-options \
    eric@exam.ple < /tmp/letter.txt

Email addresses and plain user names are subject to alternates filtering, and names only are first expanded through alias and mta-aliases. An address in angle brackets consisting only of a valid local user ‘<name>’ will be converted to a fully qualified address if either hostname is not set, or set to a non-empty value; if set to the empty value the conversion is left up to the mta. By setting expandaddr fine-grained control of recipient address types other than user names and network addresses is possible. Recipients are classified as follows:

any name that starts with a vertical bar ‘|’ character specifies a command pipe – the command string following the ‘|’ is executed and the message is sent to its standard input;
likewise, any name that consists only of hyphen-minus ‘-’ or starts with the character solidus ‘/’ or the character sequence dot solidus ‘./’ is treated as a file, regardless of the remaining content.
Any other name which contains a commercial at ‘@’ character is a network address;
Any other name which starts with a plus sign ‘+’ character is a mailbox name;
Any other name which contains a solidus ‘/’ character but no exclamation mark ‘!’ or percent sign ‘%’ character before is also a mailbox name;
What remains is treated as a network address.

This classification can be avoided by using a ‘Fcc:’ header, see “Compose mode”.

$ echo bla | s-nail -Sexpandaddr -s test ./mbox.mbox
$ echo bla | s-nail -Sexpandaddr -s test '|cat >> ./mbox.mbox'
$ echo safe | LC_ALL=C \
    s-nail -:/ -Smta=test -Sv15-compat -Sttycharset=utf8 \
      --set mime-force-sendout --set fullnames \
      -S expandaddr=fail,-all,+addr,failinvaddr -s test \
      --end-options 'Imagine John <cold@turk.ey>'

Before messages are sent they undergo editing in “Compose mode”. But many settings are static and can be set more generally. The envelope sender address for example is defined by from, and explicitly defining an originating hostname may be desirable, especially with the built-in SMTP Mail-Transfer-Agent mta. “Character sets” for outgoing message and MIME part content are configurable via sendcharsets, whereas input data is assumed to be in ttycharset. Message data will be passed over the wire in a mime-encoding, and MIME parts aka attachments need a mimetype, usually taken out of “The mime.types files”. Saving copies of sent messages in a record mailbox may be desirable – as for most mailbox folder targets “Filename transformations” will be performed. 💅

For the purpose of arranging a complete environment of settings that can be switched to with a single command or command line option there are accounts. Alternatively a flat configuration could be possible, making use of so-called variable chains which automatically pick ‘USER@HOST’ or ‘HOST’ context-dependent variants some variables support: for example addressing ‘Folder pop3://yaa@exam.ple’ would find pop3-no-apop-yaa@exam.ple, pop3-no-apop-exam.ple and pop3-no-apop in order. For more please see “On URL syntax and credential lookup” and “INTERNAL VARIABLES”.

To avoid environmental noise scripts should create a script-local environment, ideally with the command line options -: to disable configuration files in conjunction with repetitions of -S to specify variables:

$ env LC_ALL=C s-nail -:/ \
    -Sv15-compat \
    -Sttycharset=utf-8 -Smime-force-sendout \
    -Sexpandaddr=fail,-all,failinvaddr \
    -S mta=smtps://mylogin@exam.ple:465 -Ssmtp-auth=login \
    -S from=scriptreply@exam.ple \
    -s 'Subject to go' -a attachment_file \
    -Sfullnames -. \
    'Recipient 1 <rec1@exam.ple>' rec2@exam.ple \
    < content_file

As shown, scripts can “fake” a locale environment, the above specifies the all-compatible 7-bit clean LC_ALL “C”, but will nonetheless take and send UTF-8 in the message text by using ttycharset. If character set conversion is compiled in (features includes the term ‘,+iconv,’) invalid (according to ttycharset) character input data would normally cause errors; setting mime-force-sendout will instead, as a last resort, classify the input as binary data, and therefore allow message creation to be successful. (Such content can then be inspected either by installing a pipe-TYPE/SUBTYPE handler for ‘application/octet-stream’, or possibly automatically through mime-counter-evidence).

In interactive mode, introduced soon, messages can be sent by calling the mail command with a list of recipient addresses:

$ s-nail -:/ -Squiet -Semptystart -Sfullnames -Smta=test
"/var/spool/mail/user": 0 messages
? mail "Recipient 1 <rec1@exam.ple>", rec2@exam.ple
...
? # Will do the right thing (tm)
? m rec1@exam.ple rec2@exam.ple

🎀 Compose mode 🎀

If standard input is a terminal rather than the message to be sent, the user is expected to type in the message contents. In compose mode lines beginning with the character ‘~’ (in fact the value of escape) are special – these are so-called “COMMAND ESCAPES” which can be used to read in files, process shell commands, add and edit attachments and more. For example ~v or ~e will start the VISUAL text EDITOR, respectively, to revise the message in its current state, ~h allows editing of the most important message headers, with the potent ~^ custom headers can be created, for example (more specifically than with -C and customhdr). [Option]ally ~? gives an overview of most other available command escapes.

To create file-carbon-copies the special recipient header ‘Fcc:’ may be used as often as desired, for example via ~^. Its entire value (or body in standard terms) is interpreted as a folder target, after having been subject to “Filename transformations”: this is the only way to create a file-carbon-copy without introducing an ambiguity regarding the interpretation of the address, file names with leading vertical bars or commercial ats can be used. Like all other recipients ‘Fcc:’ is subject to the checks of expandaddr. Any local file and pipe command addressee honours the setting of mbox-fcc-and-pcc.

Once finished with editing the command escape ~. (see there) will call hooks, insert automatic injections and receivers, leave compose mode and send the message once it is completed. Aborting letter composition is possible with either of ~x or ~q, the latter of which will save the message in the file denoted by DEAD unless nosave is set. And unless ignoreeof is set the effect of ~. can also be achieved by typing end-of-transmission (EOT) via ‘control-D’ (‘^D’) at the beginning of an empty line, and ~q is always reachable by typing end-of-text (ETX) twice via ‘control-C’ (‘^C’).

The compose mode hooks on-compose-enter, on-compose-splice, on-compose-leave and on-compose-cleanup may be set to defined macros and provide reliable and increasingly powerful mechanisms to perform automated message adjustments dependent on message context, for example addition of message signatures (message-inject-head, message-inject-tail) or creation of additional receiver lists (also by setting autocc, autobcc). To achieve that the command digmsg may be used in order to query and adjust status of message(s). The splice hook can also make use of “COMMAND ESCAPES”. ([v15 behaviour may differ] The compose mode hooks work for forward, mail, reply and variants; resend and Resend only provide the hooks on-resend-enter and on-resend-cleanup, which are pretty restricted due to the nature of the operation.)

🌸 On reading mail, and more on interactive mode 🌸

When invoked without addressees S-nail enters interactive mode in which mails may be read. When used like that the user’s system inbox (for more on mailbox types please see the command folder) is read in and a one line header of each message therein is displayed if the variable header is set. The visual style of this summary of headers can be adjusted through the variable headline and the possible sorting criterion via autosort. Scrolling through screenfuls of headers can be performed with the command z. If the initially opened mailbox is empty S-nail will instead exit immediately (after displaying a message) unless the variable emptystart is set.

At the prompt the command list will give a listing of all available commands and help will [Option]ally give a summary of some common ones. If the [Option]al documentation strings are available (see features) one can type ‘help X’ (or ‘?X’) and see the actual expansion of ‘X’ and what its purpose is, i.e., commands can be abbreviated (note that POSIX defines some abbreviations, so that the alphabetical order of commands does not necessarily relate to the abbreviations; it is however possible to define overwrites with commandalias). These commands can also produce a more verbose output.

Messages are given numbers (starting at 1) which uniquely identify messages; the current message – the “dot” – will either be the first new message, or the first unread message, or the first message of the mailbox; the internal variable showlast will instead cause usage of the last message for this purpose. The command headers will display a screenful of header summaries containing the “dot”, whereas from will display only the summaries of the given messages, defaulting to the “dot”.

Message content can be displayed with the command type (‘t’, alias print). Here's where the variable crt comes in — it controls whether and when S-nail will use your configured PAGER for display instead of just yeeting text straight to your terminal screen. That's literally the only difference between this and the command more, which will always use the PAGER, no questions asked. The command top is different again — it'll only show you the first toplines of a message (and it might even be compressed if topsqueeze is set 🫠). Ngl your whole message-display experience can get way better if you set and adjust mime-counter-evidence — and also go peek at “HTML mail and MIME attachments” 💖.

By default the current message (the “dot”) is what gets displayed, but like with so many other commands you can absolutely hand it a fancy message specification (see “Specifying messages”). For example:

‘t:u’ displays all unread messages ✨
‘t.’ displays the “dot”
‘t 1 5’ types messages 1 and 5
‘t 1-5’ types messages 1 through 5
‘t-’ displays the previous message
‘t+’ displays the next message

The command search (a more substantial alias for from) will display a header summary of the given message specification list instead of their content. So like, the following searches for subjects:

? from '@Some subject to search for'

In the default setup all header fields of a message get typed, but you can white- or blacklist fields for a whole variety of applications using the command headerpick. Example: to restrict their display to a very restricted set for type, hit it with headerpick type retain from to cc subject. And if you wanna display all header fields of a message regardless of which ignore or retain lists are currently active, use the commands Type and Top; Show will show you the raw message content. Lowkey note that historically the global s-nail.rc not only adjusts the list of displayed headers, but also sets crt ([v15 behaviour may differ] A yet somewhat restricted). Reliable scriptable message inspection is available via digmsg 👑

Dependent on the configuration, a line editor (see the section “On terminal control and line editor”) aims at making the user experience with the many “COMMANDS” a bit nicer 💅. When reading the system inbox — or when -f (or folder) specified a mailbox explicitly prefixed with the special ‘%:’ modifier (which propagates it to a “primary system mailbox”) — then messages which have been read (see “Message states”) will automatically be moved to a “secondary mailbox”, the user's MBOX file, when the mailbox is left. That happens either by changing the active mailbox or by quitting S-nail. Fr fr, this automatic moving from a system- or primary- to the secondary mailbox is not performed when the variable hold is set. Messages can also be explicitly moved to other mailboxes, whereas copy keeps the original message. And write can be used to write out data content of specific parts of messages 🎀.

After examining a message the user can reply ‘r’ to the sender and all recipients (which will also be placed in ‘To:’ unless recipients-in-cc is set), or Reply ‘R’ exclusively to the sender(s). To comply with the receivers desired reply address, the “quadoption”s followup-to-honour and reply-to-honour should usually be set. The commands Lreply and Lfollowup know how to apply a special addressee massage — see “Mailing lists”. Dependent on the presence and value of quote, the message being replied to will be included in a quoted form. Forwarding a message will allow editing the new message: the original message will be contained in the message body, adjusted according to headerpick. It's possible to resend or Resend messages: the former adds a series of ‘Resent-’ headers, the latter will not. And different to newly created messages, editing is not possible, and no copy will be saved even with record unless the additional variable record-resent is set 👀. When sending, replying or forwarding messages, comments and full names will be stripped from recipient addresses unless the internal variable fullnames is set.

Of course messages can be deleted with ‘d’, and they can spring back into existence again via undelete, or when the S-nail session is ended via the exit or xit commands — those do a quick program termination. To end a mail processing session regularly and perform a full program exit, issue the command quit. It will, among others, move read messages to the “secondary mailbox” MBOX as necessary, discard deleted messages in the current mailbox, and update the [Option]al (see features) line editor history-file ✨. Oh and by the way — whenever the main event loop is about to look out for the next input line, it will trigger the hook on-main-loop-tick 🕰️.

🌸 HTML mail and MIME attachments 🌸

HTML-only messages become more and more common, and so many messages come bundled with a whole bouquet of MIME (Multipurpose Internet Mail Extensions) parts and attachments 💐. To get a notion of MIME types, S-nail has a default set of types built-in, and onto that the content of “The mime.types files” will be added (as configured and allowed by mimetypes-load-control). Types can also become registered with the command mimetype. And to improve interaction with the faulty MIME part declarations that real life throws at us, mime-counter-evidence will allow verification of the given assertion, plus the possible provision of an alternative, better MIME type 🔥.

Whereas a simple HTML-to-text filter for displaying HTML messages is [Option]ally supported (indicated by ‘,+filter-html-tagsoup,’ in features), MIME types other than plain text cannot be handled directly. Instead, programs need to become registered to deal with specific MIME types or file extensions. There's two flavours of that:

to prepare (re-)integrable plain text versions of their input — a mode which is called copiousoutput
to display the content externally, for example in a graphical window — the latter type is only considered by and for the command mimeview

To install a handler program for a MIME type, an according pipe-TYPE/SUBTYPE variable needs to be set; to define a handler for a file extension, pipe-EXTENSION can be used — these handlers take precedence 👑. [Option]ally, mail user agent configuration is supported (see “The Mailcap files”), and will be queried for display or quote handlers after the former ones. Type-markers registered via mimetype are the last possible source for information on how to handle a MIME type.

So like, for example: to display HTML messages integrated via the text browsers lynx(1) or elinks(1), register a MathML MIME type and enable its plain text display, and to open PDF attachments in an external PDF viewer — asynchronously, with some other magic attached:

? if "$features" !% ,+filter-html-tagsoup,
?   #set pipe-text/html='?* elinks -force-html -dump 1'
?   set pipe-text/html='?* lynx -stdin -dump -force_html'
?   # Display HTML as plain text instead
?   #set pipe-text/html=?t
? endif
? mimetype ?t application/mathml+xml mathml
? wysh set pipe-application/pdf='?&=? \
    trap "rm -f \"${MAILX_FILENAME_TEMPORARY}\"" EXIT;\
    trap "trap \"\" INT QUIT TERM; exit 1" INT QUIT TERM;\
    mupdf "${MAILX_FILENAME_TEMPORARY}"'

💌 Mailing lists 💌

Known or subscribed-to mailing lists may be flagged in the summary of headers (headline format character ‘%L’), and they gain special treatment when sending mails. The variable followup-to-honour will ensure that a ‘Mail-Followup-To:’ header is honoured when a message is being replied to (reply, followup, Lreply, Lfollowup), and followup-to controls creation of this header when creating mails — if the necessary user setup (from, sender) is available. Then it may also be created automatically, for example when list-replying via Lreply or Lfollowup, when followup or reply is used and the message's ‘Mail-Followup-To:’ is honoured, etc. 🦋

The commands mlist and mlsubscribe manage S-nail's notion of which addresses are mailing lists. With the [Option]al regular expression support, any address which contains any of the magic regular expression characters (‘^[*+?|$’; see re_format(7) or regex(7), dependent on the host system) will be compiled and used as one, possibly matching many addresses. It is not possible to escape the “magic”: in order to match special characters as-is, bracket expressions must be used, for example ‘search @subject@'[[]open bracket'’ 🙈.

? set followup-to followup-to-honour=ask-yes \
    reply-to-honour=ask-yes
? mlist a1@b1.c1 a2@b2.c2 '.*@lists\.c3$'
? mlsubscribe a4@b4.c4 exact@lists.c3

Known and subscribed lists differ in that for the latter the user's address is not part of a generated ‘Mail-Followup-To:’. There are exceptions though, for example if multiple lists are addressed and not all have the subscription attribute. When replying to a message, its list address (‘List-Post:’ header) is automatically and temporarily treated like a known mlist. And dependent on the variable reply-to-honour, an existing ‘Reply-To:’ is used instead (if it is a single address on the same domain as ‘List-Post:’) in order to accept a list administrator's wish that is supposed to have been manifested like that 💅.

For convenience and compatibility with mail programs that do not honour the non-standard M-F-T, an automatic user entry in the carbon-copy ‘Cc:’ address list of generated message can be created by setting followup-to-add-cc. This entry will be added whenever the user will be placed in the ‘Mail-Followup-To:’ list, and is not a regular addressee already. And reply-to-swap-in tries to deal with the address rewriting that many mailing-lists nowadays perform to work around DKIM / DMARC etc. standard imposed problems 😭.

🔐 Signed and encrypted messages with S/MIME 🔐

With [Option] S/MIME you get two central mechanisms: message signing and message encryption. A signed message contains some data in addition to the regular text. That data can be used to verify that the message has been sent using a valid certificate, that the sender address matches the one in the certificate, and that the message text has not been altered ✨. Signing a message does not change its regular text; it can be read regardless of whether the recipient's software is able to handle S/MIME. It's thus usually possible to sign all outgoing messages if so desired 👑.

Encryption, in contrast, makes the message text invisible for all people except those who have access to the secret decryption key. To encrypt a message, the specific recipients public encryption key must be known. It is therefore not possible to send encrypted mail to people unless their key has been retrieved from either previous communication or public key directories 🔑. And because signing is performed with private keys, and encryption with public keys, messages should always be signed before being encrypted — periodt 💖.

So a central concept of S/MIME is the certification authority (CA) — think of it as that one trusted institution that issues certificates, no cap. For every single one of those certificates you can verify it really came from the CA, as long as the CA's own certificate is already known to you beforehand. Usually a whole set of CA certificates gets delivered and installed right alongside the cryptographic library that's used on your local system, so reasonable security for S/MIME on the Internet is provided if the source that provides that library installation is trusted. 💖

You can also totally roll with a specific pool of trusted certificates if you want. If that's your vibe, set smime-ca-no-defaults so the default certificate pool doesn't get used, and point smime-ca-file and/or smime-ca-dir at a trusted pool of certificates. Just remember the golden rule: a certificate cannot be more secure than the method its CA certificate has been retrieved with. Fr fr, that's the whole thing.

This trusted pool of certificates is what the command verify uses to make sure the S/MIME messages you're looking at can actually be trusted. And if they can? Verified sender certificates that were embedded in signed messages can be saved locally with the command certsave, and then used by S-nail to encrypt further communication with these senders:

? certsave FILENAME
? set smime-encrypt-USER@HOST=FILENAME \
    smime-cipher-USER@HOST=AES256

Okay so next up: to sign outgoing messages — like, so receivers can verify where these messages actually came from — you need a personal S/MIME certificate. S-nail supports password-protected personal certificates (and keys), check smime-sign-cert for that. 💅 The section “On URL syntax and credential lookup” gives you the overview of all the possible sources of user credentials, and “S/MIME step by step” shows examplarily how a private S/MIME certificate can be obtained. In general though, if you already have that private key plus certificate “pair” sitting there, all you gotta do is set some variables:

? set smime-sign-cert=ME@exam.ple.paired \
    smime-sign-digest=SHA512 \
    smime-sign from=myname@my.host

Variables of interest for S/MIME in general are smime-ca-dir, smime-ca-file, smime-ca-flags, smime-ca-no-defaults, smime-crl-dir, smime-crl-file. For S/MIME signing, the main characters are smime-sign, smime-sign-cert, smime-sign-include-certs and smime-sign-digest. Additional variables of interest for S/MIME en- and decryption: smime-cipher and smime-encrypt-USER@HOST. Variables of secondary interest may be content-description-smime-message and content-description-smime-signature. Oh and S/MIME is available if ,+smime, is included in features. ✨

[v15 behaviour may differ] Heads up bestie: neither S/MIME signing nor encryption applies to message subjects or other header fields yet. So they may not contain sensitive information for encrypted messages, and they cannot be trusted even if the message content has been verified. 😭 When you're sending signed messages, it's recommended to repeat any important header information in the message text. You're welcome.

🦋 On URL syntax and credential lookup 🦋

For accessing protocol-specific resources, Uniform Resource Locators (URL, RFC 3986) have become, like, everywhere. Here they're expected in a “normalized” variant — not used in data exchange, but only meant as a compact, easy-to-use way of defining and representing information in a well-known notation. As such, they do not conform to any real standard. 🙈

Optional parts go in brackets [], and they're optional either because there also exist other ways to define the information, or because the part is protocol specific. Like, /path for example is used by the [Option]al Maildir folder type and the IMAP protocol, but not by POP3. And if USER and PASSWORD are included in an URL server specification, you need URL percent encoded (RFC 3986) forms — generable with urlcodec:

PROTOCOL://[USER[:PASSWORD]@]server[:port][/path]

Often “INTERNAL VARIABLES” exist in multiple versions, called “variable chains” in this document: the plain variable as well as variable-HOST and variable-USER@HOST. If a port was specified, HOST really means server:port, not server. And this USER is never in URL percent encoded form. 💀

For example — whether the hypothetical smtp://wings%3Aof@a.dove including user and password was used, or whether it was smtp://a.dove and it came from a different source — to look up the chain tls-config-pairs first tls-config-pairs-wings:of@a.dove is looked up, then tls-config-pairs-a.dove, before finally looking up the plain variable. Chain logic slay.

The logic to collect (an accounts) credential information is as follows:

A user is always required. If no USER has been given in the URL, the variables user-HOST and user are looked up. Afterwards, when enforced by the [Option]al variables netrc-lookup-HOST or netrc-lookup, “The .netrc file” of the user will be searched for a HOST specific entry which provides a login name: only unambiguous entries are used (one possible matching entry for HOST).

If there is still no USER then the verified LOGNAME, known to be a valid user on the current host, is used.

Authentication: unless otherwise noted the chain PROTOCOL-auth-USER@HOST, PROTOCOL-auth-HOST, PROTOCOL-auth is checked, falling back to a protocol-specific default as necessary.
If no PASSWORD has been given in the URL, then if the USER has been found through the [Option]al netrc-lookup, that may have also provided the password. Otherwise the chain password-USER@HOST, password-HOST, password is looked up.

Thereafter the (now complete) [Option]al chain netrc-lookup-USER@HOST, netrc-lookup-HOST, netrc-lookup is checked — if set, the netrc cache is searched for a password only (multiple user accounts for a single machine may exist as well as a fallback entry without user but with a password).

If at that point there is still no password available, but the (protocols') chosen authentication type requires a password, then in interactive mode the user will be prompted on the terminal. 🫶

Note: S/MIME verification works relative to the values found in the From: (or Sender:) header field(s), which means the values of smime-sign, smime-sign-cert, smime-sign-include-certs and smime-sign-digest will not be looked up using the USER and HOST chains from above, but instead use the corresponding values from the message that is being worked on. If no address matches we assume and use the setting of from. In unusual cases multiple and different USER and HOST combinations may therefore be involved — on the other hand those unusual cases become possible. The usual case is as short as:

set mta=smtp://USER:PASS@HOST smtp-use-starttls \
    smime-sign smime-sign-cert=+smime.pair \
    from=myname@my.host

The section “EXAMPLES” contains complete example configurations. 👑

🔥 Encrypted network communication 🔥

[Option] SSL (Secure Sockets Layer) aka its successor TLS (Transport Layer Security) are protocols which aid in securing communication by providing a safely initiated and encrypted network connection. A central concept of TLS are certificates: as part of each network connection setup a (set of) certificates will be exchanged through which the identity of the network peer can be cryptographically verified. If possible the TLS/SNI (ServerNameIndication) extension will be enabled to allow servers fine-grained control over the certificates being used. Then a locally installed pool of trusted certificates gets inspected, and verification will succeed if it contains a(n in)direct signer of the presented certificate(s). 🎀

The local pool of trusted so-called CA (Certification Authority) certificates is usually delivered with and used along the TLS library. A custom pool of trusted certificates can be selected by pointing tls-ca-file and/or (with special preparation) tls-ca-dir to the desired location; setting tls-ca-no-defaults in addition will avoid additional inspection of the default pool. And again, the rule that never misses: a certificate cannot be more secure than the method its CA certificate has been retrieved with. For inspection or other purposes, the certificate of a server (as seen when connecting to it) can be fetched with the command tls (port can usually be the protocol name, too, and tls-verify is taken into account here):

$ s-nail -vX 'tls certchain SERVER-URL[:PORT]; x'

A local pool of CA certificates is not strictly necessary though — server certificates can also be verified via their fingerprint. 💅 For this a message digest will be calculated and compared against the variable chain tls-fingerprint, and verification will succeed if the fingerprint matches. The message digest (algorithm) can be configured via the variable chain tls-fingerprint-digest; tls can again be used:

$ s-nail -X 'wysh set verbose; tls fingerprint SERVER-URL[:PORT]; x'

It depends on the used protocol whether encrypted communication is possible, and which configuration steps have to be taken to enable it. Some protocols, like POP3S, are implicitly encrypted; others, like POP3, can upgrade a plain text connection if so requested. For example, to use the STLS that POP3 offers, (a member of) the variable (chain) pop3-use-starttls needs to be set — with convenience via shortcut:

shortcut encpop1 pop3s://pop1.exam.ple

shortcut encpop2 pop3://pop2.exam.ple
set pop3-use-starttls-pop2.exam.ple

set mta=smtps://smtp.exam.ple:465
set mta=smtp://smtp.exam.ple smtp-use-starttls

Normally that is all there is to do, given that TLS libraries try to provide safe defaults — but plenty of knobs exist to adjust settings. 🌈 For example certificate verification settings can be fine-tuned via tls-ca-flags, and the TLS configuration basics are accessible via tls-config-pairs — for example to control protocol versions or cipher lists. In the past, hints on how to restrict the set of protocols to highly secure ones were indicated, but as of the time of this writing the list of protocols or ciphers may need to become relaxed in order to be able to connect to some servers. The following example allows connecting to a “Lion” that uses OpenSSL 0.9.8za from June 2014 (refer to “INTERNAL VARIABLES” for more on variable chains):

wysh set tls-config-pairs-lion@exam.ple='MinProtocol=TLSv1.1,\
    CipherString=TLSv1.2:!aNULL:!eNULL:\
      ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:\
      DHE-RSA-AES256-SHA:@STRENGTH'

The OpenSSL program ciphers(1) is literally the one to check out when you're building a custom cipher list, bestie — go read it, it ate. The variables you'll actually care about for TLS in general are tls-ca-dir, tls-ca-file, tls-ca-flags, tls-ca-no-defaults, tls-config-file, tls-config-module, tls-config-pairs, tls-crl-dir, tls-crl-file, tls-rand-file and also tls-verify. Also peek at tls-features. Oh and heads up: TLS is only available if +tls is included in features. 💅

🌈 Character sets 🌈

[Option] So the user's locale environment gets detected by looking at the LC_ALL environment variable. The internal variable ttycharset gets set to the detected terminal character set accordingly, and that's why it shows up in the output of commands like set and varshow. This character set is the target when we're trying to display data, and user input data is expected to be in this character set too. ✨

When creating messages, their character input data gets classified. 7-bit clean text data and attachments get classified as charset-7bit. 8-bit data will [Option]ally be converted into members of sendcharsets until a character set conversion succeeds. charset-8bit is the implied default last member of this list. If no 8-bit character set is capable of representing the input data, no message will be sent, and its text will optionally be saved in DEAD. If that's just not acceptable — say, in script environments — mime-force-sendout can be set to force sending of non-convertible data as application/octet-stream classified binary content instead: like this, receivers still have the option to inspect message content (for example via mime-counter-evidence). If the [Option]al character set conversion isn't available (features misses ,+iconv,), then ttycharset is the only supported character set for non 7-bit clean data, and it's simply assumed it can be used to exchange 8-bit messages. 😌

ttycharset may also be given an explicit value to send mail in a completely "faked" locale environment, which can be used to generate and send, for example, 8-bit UTF-8 input data in a pure 7-bit US-ASCII LC_ALL=C environment (there's an example of this in the section "On sending mail, and non-interactive mode"). Doing that doesn't mean much beside that, though, since several aspects of the real character set are implied by the locale environment of the system, which stays unaffected by ttycharset. 🦋

Classifying 7-bit clean data as charset-7bit is a whole problem if the input character set (ttycharset) is a multibyte character set that is itself 7-bit clean. For example, the Japanese character set ISO-2022-JP is, but it's capable of encoding the rich set of Japanese Kanji, Hiragana and Katakana characters: in order to notify receivers of this character set, the mail message must be MIME encoded so that the character set ISO-2022-JP can be advertised, otherwise an invalid email message would result! 😭 To achieve this, the variable charset-7bit can be set to ISO-2022-JP. (Today a better approach regarding email is the usage of UTF-8, which uses 8-bit bytes for non-US-ASCII data.) 👑

When replying to a message and the variable reply-in-same-charset is set, the character set of the message being replied to is tried first as a target character set (still being a subject of charsetalias filtering, however). Another opportunity is sendcharsets-else-ttycharset to reflect the user's locale environment automatically — it will treat ttycharset as an implied member of (an unset) sendcharsets. 🎀

[Option] When reading messages, their text data is converted into ttycharset as necessary in order to display them on the user's terminal. Unprintable characters and invalid byte sequences are detected and replaced by substitution characters. Character set mappings for source character sets can be established with charsetalias, which may be handy to work around faulty or incomplete character set catalogues (one could, for example, add a missing LATIN1 to ISO-8859-1 mapping), or to enforce treatment of one character set as another one ("interpret LATIN1 as CP1252"). Also see charset-unknown-8bit to deal with another hairy aspect of message interpretation. 🙈

In general, if a message saying "cannot convert from a to b" appears, either some characters are not appropriate for the currently selected (terminal) character set, or the needed conversion isn't supported by the system. In the first case, it's necessary to set an appropriate LC_CTYPE locale and/or the variable ttycharset. The best results are usually achieved when running in a UTF-8 locale on a UTF-8 capable terminal, in which case the full Unicode spectrum of characters is available. In this setup, characters from various countries can be displayed, while it's still possible to use more simple character sets for sending to retain maximum compatibility with older mail clients. 💖

On the other hand, the POSIX standard defines a locale-independent 7-bit "portable character set" that should be used when overall portability is an issue; the even more restricted subset named "portable filename character set" consists of A-Z, a-z, 0-9, period ., underscore _ and hyphen-minus -. ⭐

🎀 Message states 🎀

S-nail differentiates in between several message states; the current state gets reflected in the summary of headers if the attrlist of the configured headline allows, and "Specifying messages" dependent on their state is possible. When operating on the system inbox, or in any other "primary system mailbox", special actions — like the automatic moving of messages to the "secondary mailbox" MBOX — may be applied when the mailbox is left (also implicitly by program termination, unless the command exit was used). However, because this may be irritating to users which are used to "more modern" mail-user-agents, the provided global s-nail.rc template sets the internal hold and keepsave variables in order to suppress this behaviour. 🫶

new — Message has neither been viewed nor moved to any other state. Such messages are retained even in the "primary system mailbox".
unread — Message has neither been viewed nor moved to any other state, but the message was present already when the mailbox has been opened last: such messages are retained even in the "primary system mailbox".
read — The message has been processed by one of the following commands: ~f, ~m, ~F, ~M, copy, mbox, next, pipe, Print, print, top, Type, type, undelete. The commands dp and dt will always try to automatically "step" and type the "next" logical message, and may thus mark multiple messages as read; the delete command will do so if the internal variable autoprint is set.

Except when the exit command is used, messages that are in a "primary system mailbox" and are in read state when the mailbox is left will be saved in the "secondary mailbox" MBOX unless the internal variable hold is set. 💀

deleted — The message has been processed by one of the following commands: delete, dp, dt. Only undelete can be used to access such messages.
preserved — The message has been processed by a preserve command and it will be retained in its current location.
saved — The message has been processed by one of the following commands: save or write. Unless when the exit command is used, messages that are in a "primary system mailbox" and are in saved state when the mailbox is left will be deleted; they will be saved in the "secondary mailbox" MBOX when the internal variable keepsave is set.

In addition to these message states, flags — which otherwise have no technical meaning in the mail system except allowing special ways of addressing them when "Specifying messages" — can be set on messages. These flags are saved with messages and are thus persistent, and are portable between a set of widely used MUAs. 🔥

answered — Mark messages as having been answered.
draft — Mark messages as being a draft.
flag — Mark messages which need special attention.

🦋 Specifying messages 🦋

[Only new quoting rules] COMMANDS which take "Message list arguments" — such as search, type, copy, and delete — can perform actions on a number of messages at once. Specifying invalid messages, or using illegal syntax, will cause errors to be reported through the "INTERNAL VARIABLES" !, ^ERR and companions, as well as the command exit status ?. 😤

For example, delete 1 2 deletes the messages 1 and 2, whereas delete 1-5 will delete the messages 1 through 5. In sorted or threaded mode (see the sort command), delete 1-5 will delete the messages that are located between (and including) messages 1 through 5 in the sorted/threaded order, as shown in the headers summary. ✨

Errors can, for example, be ^ERR-BADMSG when requesting an invalid message, ^ERR-NOMSG if no applicable message can be found, ^ERR-CANCELED for missing informational data (mostly thread-related). ^ERR-INVAL for invalid syntax as well as ^ERR-IO for input/output errors can happen. The following special message names exist, bestie: 💅

. — The current message, the so-called "dot".
; — The message that was previously the current message; needs to be quoted.
, — The parent message of the current message, that is the message with the Message-ID given in the In-Reply-To: field or the last entry of the References: field of the current message.
- — The previous undeleted message, or the previous deleted message for the undelete command; in sorted or threaded mode, the previous such message in the according order.
+ — The next undeleted message, or the next deleted message for the undelete command; in sorted or threaded mode, the next such message in the according order.
^ — The first undeleted message, or the first deleted message for the undelete command; in sorted or threaded mode, the first such message in the according order.
$ — The last message; in sorted or threaded mode, the last such message in the according order. Needs to be quoted.
&x — In threaded sort mode, selects the message addressed with x, where x is any other message specification, and all messages from the thread that begins at it. Otherwise it's identical to x. If x is omitted, the thread beginning with the current message is selected.
* — All messages.
` — literally all the messages that were in the “Message list arguments” of the previous command, bestie 💫 and yeah, it needs to be quoted. (A genuinely convenient way to read all new messages: select them via from :n, as below, and then read them in order with the default command — which is next — simply by successively typing ‘’; for this trick to work showlast` must be set. iykyk.)
x-y — an inclusive range of message numbers 🎀 Selectors that may also be used as endpoints include any of .;-+^$.
address — a case-insensitive “any substring matches” search against the From: header, which will match addresses (too) even if showname is set (and POSIX says “any address as shown in a header summary shall be matchable in this form”, so there's that 🌸). However — if the allnet variable is set, only the local part of the address is evaluated for the comparison, not ignoring case, and the setting of showname is completely ignored. For finer control and match boundaries, use the @ search expression instead.
/string — all messages that contain string in the subject field (case ignored according to locale). Also peek at the searchheaders variable. If string is empty, the string from the previous specification of that type is used again ✨
[@name-list]@expr — all messages that contain the given case-insensitive search expression; if the [Option]al regular expression support is available, expr will be interpreted as (an extended) one if any of the “magic regular expression characters” is seen 👀 If the optional @name-list part is missing, the search is restricted to the subject field body — but otherwise name-list specifies a comma-separated list of header fields to search, for example

'@to,from,cc@Someone i ought to know'

In order to search for a string that includes a ‘@’ (commercial at) character, the name-list is effectively non-optional, but may be given as the empty string. Also, specifying an empty search expression will effectively test for existence of the given header fields. Some special header fields may be abbreviated: ‘f’, ‘t’, ‘c’, ‘b’ and ‘s’ will match ‘From’, ‘To’, ‘Cc’, ‘Bcc’ and ‘Subject’, respectively, and case-insensitively 🫶 [Option]ally, and just like expr, name-list will be interpreted as (an extended) regular expression if any of the “magic regular expression characters” is seen.

The special names ‘header’ or ‘<’ can be used to search in (all of) the header(s) of the message, and the special names ‘body’ or ‘>’ and ‘text’ or ‘=’ will perform full text searches — whereas the former searches only the body, the latter also searches the message header ([v15 behaviour may differ] this mode yet brute force searches over the entire decoded content of messages, including administrativa strings 👑).

This specification performs full text comparison, but even with regular expression support it is almost impossible to write a search expression that safely matches only a specific address domain 😭. To request that the body content of the header is treated as a list of addresses, and to strip those down to the plain email address which the search expression is to be matched against, prefix the effective name-list with a tilde ‘~’:

'@~f,c@@a\.safe\.domain\.match$'

:c — all messages of state or with matching condition ‘c’, where ‘c’ is one or multiple of these colon modifiers 💅
- a — answered messages (cf. the variable markanswered).
- d — ‘deleted’ messages (for the undelete and from commands only).
- f — flagged messages.
- L — messages with receivers that match mlsubscribed addresses.
- l — messages with receivers that match mlisted addresses.
- n — ‘new’ messages.
- o — old messages (any not in state ‘read’ or ‘new’).
- r — ‘read’ messages.
- S — [Option] messages with unsure spam classification (see “Handling spam”).
- s — [Option] messages classified as spam.
- t — messages marked as draft.
- u — ‘unread’ messages.

[Option] IMAP-style SEARCH expressions may also be used 🔥 These consist of keywords and criterions, and because “Message list arguments” are split into tokens according to “Shell-style argument quoting”, it is necessary to quote the entire IMAP search expression in order to ensure that it remains a single token, mmkay? This addressing mode is available with all types of mailbox folders; S-nail will perform the search locally as necessary 💖 Strings must be enclosed by double quotation marks ‘"’ in their entirety if they contain whitespace or parentheses; within the quotes, only reverse solidus ‘\’ is recognized as an escape character. All string searches are case-insensitive 🌈

When the description says that the “envelope” representation of an address field is used, that means the search string is checked against both a list constructed as

'("name" "source" "local-part" "domain-part")'

for each address, and the addresses without real names from the respective header field. These search expressions can be nested using parentheses — see below for examples 🦋

(criterion) — all messages that satisfy the given criterion.
(criterion1 criterion2 ... criterionN) — all messages that satisfy all of the given criteria.
(or criterion1 criterion2) — all messages that satisfy either criterion1 or criterion2, or both. To connect more than two criteria using ‘or’ specifications, you have to nest them with additional parentheses, as with ‘(or a (or b c))’, since ‘(or a b c)’ really means ‘((a or b) and c)’. For a simple ‘or’ operation of independent criteria on the lowest nesting level, it is possible to achieve similar effects by using three separate criteria, as with ‘(a) (b) (c)’ 🎀
(not criterion) — all messages that do not satisfy criterion.
(bcc "string") — all messages that contain string in the envelope representation of the ‘Bcc:’ field.
(cc "string") — all messages that contain string in the envelope representation of the ‘Cc:’ field.
(from "string") — all messages that contain string in the envelope representation of the ‘From:’ field.
(subject "string") — all messages that contain string in the ‘Subject:’ field.
(to "string") — all messages that contain string in the envelope representation of the ‘To:’ field.
(header name "string") — all messages that contain string in the specified ‘Name:’ field.
(body "string") — all messages that contain string in their body.
(text "string") — all messages that contain string in their header or body.
(larger size) — all messages that are larger than size (in bytes).
(smaller size) — all messages that are smaller than size (in bytes).
(before date) — all messages that were received before date, which must be in the form ‘d[d]-mon-yyyy’, where ‘d’ denotes the day of the month as one or two digits, ‘mon’ is the name of the month — one of ‘Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec’ — and ‘yyyy’ is the year as four digits, for example ‘28-Dec-2012’ 📅
(on date) — all messages that were received on the specified date.
(since date) — all messages that were received since the specified date.
(sentbefore date) — all messages that were sent on the specified date.
(senton date) — all messages that were sent on the specified date.
(sentsince date) — all messages that were sent since the specified date.
() — the same criterion as for the previous search. This specification cannot be used as part of another criterion 🙈 If the previous command line contained more than one independent criterion, then the last of those criteria is used.

✨ On terminal control and line editor ✨

[Option] Terminal control through one of the standard Unix libraries — Termcap Access Library (libtermcap, -ltermcap) or Terminal Information Library (libterminfo, -lterminfo) — may be available 🌸 For the TERMinal defined in the environment, interactive usage aspects, for example “Coloured display”, and insight of cursor and function keys for the Mailx-Line-Editor (MLE), will be enhanced or enabled. Library interaction can be disabled on a per-invocation basis via termcap-disable, whereas the internal variable termcap is always used as a preferred source of terminal capabilities 👑 (For a usage example see the “FAQ” entry “Not "defunctional", but the editor key does not work”.)

[Option] The built-in Mailx-Line-Editor (MLE) should work in all environments which comply to the ISO C standard ISO/IEC 9899/AMD1:1995 (“ISO C90, Amendment 1”), and will support wide glyphs if possible (the necessary functionality had been removed from ISO C, but was included in X/Open Portability Guide Issue 4 (“XPG4”)) 💜 Usage of a line editor in interactive mode can be prevented by setting line-editor-disable. Especially if the [Option]al terminal control support is missing, setting entries in termcap will help shall the MLE misbehave — see there for more. The MLE can support a little bit of colour 🎨

[Option] If the history feature is available, then input from line editor prompts will be saved in a history list that can be searched in and be expanded from 🦋 Such saving can be prevented by prefixing input with any amount of whitespace. Aspects of history — like allowed content and maximum size, as well as whether history shall be saved persistently — can be configured with the internal variables history-file, history-gabby, history-gabby-persist and history-size. There also exists the macro hook on-history-addition which can be used to apply finer control on what enters history 💖

okay so the MLE (that's the line editor, bestie) supports a whole set of editing and control commands. By default, as many of them as possible get assigned to a set of single-letter control codes, and those should work on literally any terminal — you generate them by holding down the "control" key while pressing the key of your desire, like Ctrl+D for control-D. Now, if the [Option]al bind command is available, then you can also access the MLE commands freely by assigning the command name — which is shown in parenthesis in the list below — to any key-sequence you want, and the MLE will instead and also use bind to establish its built-in key bindings (more of them if the [Option]al terminal control is available). That whole thing can then be suppressed completely by setting line-editor-no-defaults. Also: "Shell-style argument quoting" notation is used in the following 💅

\cA — Go to the start of the line (mle-go-home).
\cB — Move the cursor backward one character (mle-go-bwd).
\cC — raise(3) SIGINT (mle-raise-int).
\cD — Forward delete the character under the cursor; quits S-nail if used on the empty line unless the internal variable ignoreeof is set (mle-del-fwd).
\cE — Go to the end of the line (mle-go-end).
\cF — Move the cursor forward one character (mle-go-fwd).
\cG — Cancel current operation, full reset. If there's an active history search or tabulator expansion then this command resets that first, reverting to the former line content — so you need a second reset for a full reset in that case (mle-reset).
\cH — Backspace: backward delete one character (mle-del-bwd).
\cI — [Only new quoting rules] Horizontal tabulator: try to expand the word before the cursor, supporting the usual "Filename transformations" (mle-complete; this is affected by mle-quote-rndtrip and line-editor-cpl-word-breaks).
\cJ — Newline: commit the current line (mle-commit).
\cK — Cut all characters from the cursor to the end of the line (mle-snarf-end).
\cL — Repaint the line (mle-repaint).
\cN — [Option] Go to the next history entry (mle-hist-fwd).
\cO — ([Option]ally context-dependent) Invokes the command dt.
\cP — [Option] Go to the previous history entry (mle-hist-bwd).
\cQ — Toggle roundtrip mode shell quotes, where produced, on and off (mle-quote-rndtrip). Heads up: this setting is temporary and will be forgotten once the command line is committed; also see shcodec.
\cR — [Option] Complete the current line from (the remaining) older history entries (mle-hist-srch-bwd).
\cS — [Option] Complete the current line from (the remaining) newer history entries (mle-hist-srch-fwd).
\cT — Paste the snarf buffer (mle-paste).
\cU — The same as \cA followed by \cK (mle-snarf-line).
\cV — Prompts for a Unicode character (hexadecimal number without prefix, see vexpr) to be inserted (mle-prompt-char). Note that this command needs to be assigned to a single-letter control code in order to become recognized and executed during input of a key-sequence (only three single-letter control codes can be used for that shortcut purpose); this control code is then special-treated and thus cannot be part of any other sequence (because it will trigger the mle-prompt-char function immediately).
\cW — Cut the characters from the one preceding the cursor to the preceding word boundary (mle-snarf-word-bwd).
\cX — Move the cursor forward one word boundary (mle-go-word-fwd).
\cY — Move the cursor backward one word boundary (mle-go-word-bwd).
\cZ — raise(3) SIGTSTP (mle-raise-tstp).
\c[ — Escape: reset a possibly used multibyte character input state machine and [Option]ally a lingering, incomplete key binding (mle-cancel). This command needs to be assigned to a single-letter control code in order to become recognized and executed during input of a key-sequence (only three single-letter control codes can be used for that shortcut purpose). This control code may also be part of a multi-byte sequence, but if a sequence is active and the very control code is currently also an expected input, then the active sequence takes precedence and will consume the control code.
\c\ — ([Option]ally context-dependent) Invokes the command z+.
\c] — ([Option]ally context-dependent) Invokes the command z$.
\c^ — ([Option]ally context-dependent) Invokes the command z0.
\c_ — Cut the characters from the one after the cursor to the succeeding word boundary (mle-snarf-word-fwd).
\c? — Backspace: mle-del-bwd.
– — mle-bell: ring the audible bell.
– — [Option] mle-clear-screen: move the cursor home and clear the screen.
– — mle-fullreset: different to mle-reset, this will immediately reset a possibly active search etc.
– — mle-go-screen-bwd: move the cursor backward one screen width.
– — mle-go-screen-fwd: move the cursor forward one screen width.
– — mle-raise-quit: raise(3) SIGQUIT.

🎨 Coloured display 🎨

[Option] Colours and font attributes through ANSI a.k.a. ISO 6429 SGR (select graphic rendition) escape sequences are optionally supported, and honestly? iconic. Usage of colours and font attributes solely depends upon the capability of the detected terminal type (TERM), and as fine-tuned through termcap. You manage colours and font attributes with the multiplexer command colour, and uncolour removes the given mappings. Setting colour-disable suppresses usage of colour and font attribute sequences, while leaving established mappings unchanged.

Whether actually applicable colour and font attribute sequences should also be generated when output is going to be paged through the external PAGER (also see crt) depends upon the setting of colour-pager, because pagers usually need to be configured in order to support ISO escape sequences. Knowledge of some widely used pagers is however built-in, and in a clean environment it's often enough to simply set colour-pager; please refer to that variable for more on this topic 🫶

It might make sense to conditionalize colour setup on interactive mode via if ('terminal' indeed means "interactive"):

if terminal && "$features" =% ,+colour,
  colour iso view-msginfo ft=bold,fg=green
  colour iso view-header ft=bold,fg=red (from|subject) # regex
  colour iso view-header fg=red

  uncolour iso view-header from,subject
  colour iso view-header ft=bold,fg=magenta,bg=cyan
  colour 256 view-header ft=bold,fg=208,bg=230 "subject,from"
  colour mono view-header ft=bold
  colour mono view-header ft=bold,ft=reverse subject,from
endif

🚫 Handling spam 🚫

[Option] S-nail can make use of several spam interfaces for the purpose of identification of, and, in general, dealing with spam messages. A precondition of most commands in order to function is that the spam-interface variable is set to one of the supported interfaces. "Specifying messages" that have been identified as spam is possible via their (volatile) is-spam state by using the :s and :S specifications, and their attrlist entries will be used when displaying the headline in the summary of headers.

spamrate rates the given messages and sets their is-spam flag accordingly. If the spam interface offers spam scores these can be shown in headline by using the format %$.
spamham, spamspam and spamforget will interact with the Bayesian filter of the chosen interface and learn the given messages as "ham" or "spam", respectively; the last command can be used to cause "unlearning" of messages; it adheres to their current is-spam state and thus reverts previous teachings.
spamclear and spamset will simply set and clear, respectively, the mentioned volatile is-spam message flag, without any interface interaction.

The spamassassin(1) based spam-interface spamc requires a running instance of the spamd(1) server in order to function, started with the option --allow-tell shall Bayesian filter learning be possible.

$ spamd -i localhost:2142 -i /tmp/.spamsock -d [-L] [-l]
$ spamd --listen=localhost:2142 --listen=/tmp/.spamsock \
    --daemonize [--local] [--allow-tell]

Thereafter S-nail can make use of these interfaces:

$ s-nail -Sspam-interface=spamc -Sspam-maxsize=500000 \
    -Sspamc-command=/usr/local/bin/spamc \
    -Sspamc-arguments="-U /tmp/.spamsock" -Sspamc-user=
or
$ s-nail -Sspam-interface=spamc -Sspam-maxsize=500000 \
    -Sspamc-command=/usr/local/bin/spamc \
    -Sspamc-arguments="-d localhost -p 2142" -Sspamc-user=

Using the generic filter approach allows usage of programs like bogofilter(1). Here's an example, requiring it to be accessible via PATH:

$ s-nail -Sspam-interface=filter -Sspam-maxsize=500000 \
    -Sspamfilter-ham="bogofilter -n" \
    -Sspamfilter-noham="bogofilter -N" \
    -Sspamfilter-nospam="bogofilter -S" \
    -Sspamfilter-rate="bogofilter -TTu 2>/dev/null" \
    -Sspamfilter-spam="bogofilter -s" \
    -Sspamfilter-rate-scanscore="1;^(.+)$"

Because messages must exist on local storage in order to be scored (or used for Bayesian filter training), it is possibly a good idea to perform the local spam check last. Spam can be checked automatically when opening specific folders by setting a specialized form of the internal variable folder-hook.

define spamdelhook {
  # Server side DCC
  spamset (header x-dcc-brand-metrics "bulk")
  # Server-side spamassassin(1)
  spamset (header x-spam-flag "YES")
  del :s # TODO we HAVE to be able to do `spamrate :u ! :sS'
  move :S +maybe-spam
  spamrate :u
  del :s
  move :S +maybe-spam
}
set folder-hook-SOMEFOLDER=spamdelhook

See also the documentation for the variables spam-interface, spam-maxsize, spamc-command, spamc-arguments, spamc-user, spamfilter-ham, spamfilter-noham, spamfilter-nospam, spamfilter-rate and spamfilter-rate-scanscore ✨

💬 COMMANDS 💬

okay so bestie, S-nail reads input in lines — one line at a time, that's the whole vibe. And here's a cute little trick: an unquoted reverse solidus \ sitting at the end of a command line “escapes” the newline character 😳 — it gets yeeted, and the next line of input becomes a follow-up line, with all leading whitespace removed. Once an entire line is completed, the whitespace characters space, tabulator, newline, plus whatever the variable ifs defines, all get trimmed off the beginning and end. And listen — if you put any whitespace characters at the beginning of a line, that prevents a possible addition of the command line to the [Option]al history. sneaky but true 💅

The beginning of such input lines then gets scanned for the name of a known command ✨ Command names may be abbreviated, in which case the first command that matches the given prefix will be used — so like, prefix matching, first match wins, no cap. “Command modifiers” may prefix a command to modify its behaviour. A name may also be a commandalias, which will become expanded until no more expansion is possible. Once the command that shall be executed is known, the remains of the input line get interpreted according to command-specific rules, documented in the following. 🫶

This behaviour is different to the sh(1)ell, which is a programming language with syntactic elements of clearly defined semantics, and therefore capable to sequentially expand and evaluate individual elements of a line. Like, ? set one=value two=$one for example will never possibly assign value to one, because the variable assignment is performed no sooner but by the command (set), long after the expansion happened. it's giving "order of operations but make it chaos" 😭

A list of all commands in lookup order is dumped by the command list. [Option]ally the command help (or ?), when given an argument, will show a documentation string for the command matching the expanded argument — as in ?t, which should be a shorthand of ?type ✨ With these documentation strings both commands support a more verbose listing mode which includes the argument type of the command and other information which applies; a handy suggestion might thus be:

? define __xv {
  # Before v15: need to enable sh(1)ell-style on _entire_ line!
  localopts yes;wysh set verbose;ignerr eval "${@}";return ${?}
}
? commandalias xv '\call __xv'
? xv help set

🎀 Command modifiers 🎀

Commands may be prefixed by none to multiple command modifiers 👑 Some command modifiers can be used with a restricted set of commands only, and the verbose version of list will ([Option]ally) show which modifiers apply.

The modifier reverse solidus \, to be placed first, prevents commandalias expansions on the remains of the line, for example \echo will always evaluate the command echo, even if an (command)alias of the same name exists. commandalias content may itself contain further command modifiers, including an initial reverse solidus to prevent further expansions.
The modifier ignerr indicates that any error generated by the following command should be ignored by the state machine and not cause a program exit with enabled errexit or for the standardized exit cases in posix mode. ?, one of the “INTERNAL VARIABLES”, will be set to the real exit status of the command regardless. 💖
local will alter the called command to apply changes only temporarily, local to block-scope, and can thus only be used inside of a defined macro or an account definition. Specifying it implies the modifier wysh. Local variables will not be inherited by macros deeper in the call chain, and all local settings will be garbage collected once the local scope is left. To record and unroll changes in the global scope use the command localopts.
scope does yet not implement any functionality. (iconic of it honestly 💀)
u does yet not implement any functionality. (also slaying in the "does nothing" department 🙈)
Some commands support the vput modifier: if used, they expect the name of a variable, which can itself be a variable, i.e., shell expansion is applied, as their first argument, and will place their computation result in it instead of the default location (it is usually written to standard output).

The given name will be tested for being a valid sh(1) variable name, and may therefore only consist of upper- and lowercase characters, digits, and the underscore; the hyphen-minus may be used as a non-portable extension; digits may not be used as first, hyphen-minus may not be used as last characters. In addition the name may either not be one of the known “INTERNAL VARIABLES”, or must otherwise refer to a writable (non-boolean) value variable. The actual put operation may fail nonetheless, for example if the variable expects a number argument only a number will be accepted. Any error during these operations causes the command as such to fail, and the error number ! will be set to ^ERR-NOTSUP, the exit status ? should be set to -1, but some commands deviate from the latter, which is documented. 😤

Last, but not least, the modifier wysh can be used for some old and established commands to choose the new “Shell-style argument quoting” rules over the traditional “Old-style argument quoting”. This modifier is implied if v15-compat is set to a non-empty value. ⭐

🌸 Old-style argument quoting 🌸

[v15 behaviour may differ] This section documents the traditional and POSIX standardized style of quoting non-message list arguments to commands which expect this type of arguments: whereas still used by the majority of such commands, the new “Shell-style argument quoting” may be available even for those via wysh, one of the “Command modifiers”. Nonetheless care must be taken, because only new commands have been designed with all the capabilities of the new quoting rules in mind, which can, for example generate control characters. 👀

An argument can be enclosed between paired double-quotes "argument" or single-quotes 'argument'; any whitespace, shell word expansion, or reverse solidus characters (except as described next) within the quotes are treated literally as part of the argument. A double-quote will be treated literally within single-quotes and vice versa. Inside such a quoted string the actually used quote character can be used nonetheless by escaping it with a reverse solidus \, as in "y\"ou".
An argument that is not enclosed in quotes, as above, can usually still contain space characters if those spaces are reverse solidus escaped, as in you\ are.
A reverse solidus outside of the enclosing quotes is discarded and the following character is treated literally as part of the argument.

🦋 Shell-style argument quoting 🦋

sh(1)ell-style, and therefore POSIX standardized, argument parsing and quoting rules are used by most commands. [v15 behaviour may differ] Most new commands only support these new rules and are flagged [Only new quoting rules], some elder ones can use them with the command modifier wysh; in the future only this type of argument quoting will remain. periodt. 💅

A command line is parsed from left to right and an input token is completed whenever an unquoted, otherwise ignored, metacharacter is seen. Metacharacters are vertical bar |, ampersand &, semicolon ;, as well as all characters from the variable ifs, and / or space, tabulator, newline. The additional metacharacters left and right parenthesis (, ) and less-than and greater-than signs <, > that the sh(1) supports are not used, and are treated as ordinary characters: for one these characters are a vivid part of email addresses, and it seems highly unlikely that their function will become meaningful to S-nail. 🎀

Compatibility note: [v15 behaviour may differ] Please note that even many new-style commands do not yet honour ifs to parse their arguments: whereas the sh(1)ell is a language with syntactic elements of clearly defined semantics, S-nail parses entire input lines and decides on a per-command base what to do with the rest of the line. This also means that whenever an unknown command is seen all that S-nail can do is cancellation of the processing of the remains of the line.

It also often depends on an actual subcommand of a multiplexer command how the rest of the line should be treated, and until v15 we are not capable to perform this deep inspection of arguments. Nonetheless, at least the following commands which work with positional parameters fully support ifs for an almost shell-compatible field splitting: call, call_if, read, vpospar, xcall.

Any unquoted number sign # at the beginning of a new token starts a comment that extends to the end of the line, and therefore ends argument processing. An unquoted dollar sign $ will cause variable expansion of the given name, which must be a valid sh(1)ell-style variable name (see vput): “INTERNAL VARIABLES” as well as “ENVIRONMENT” (shell) variables can be accessed through this mechanism, brace enclosing the name is supported (i.e., to subdivide a token). 🔥

Whereas the metacharacters space, tabulator, newline only complete an input token, vertical bar |, ampersand & and semicolon ; also act as control operators and perform control functions. For now supported is semicolon ;, which terminates a single command, therefore sequencing the command line and making the remainder of the line a subject to reevaluation. With sequencing, multiple command argument types and quoting rules may therefore apply to a single line, which can become problematic before v15: e.g., the first of the following will cause surprising results. 😭

? echo one; set verbose; echo verbose=$verbose.
? echo one; wysh set verbose; echo verbose=$verbose.

Quoting is a mechanism that will remove the special meaning of metacharacters and reserved words, and will prevent expansion. There are four quoting mechanisms: the escape character, single-quotes, double-quotes and dollar-single-quotes:

The literal value of any character can be preserved by preceding it with the escape character reverse solidus \.
Arguments which are enclosed in 'single-quotes' retain their literal value. A single-quote cannot occur within single-quotes.
The literal value of every character chillin' inside "double-quotes" is kept exactly as-is, with one exception bestie: the dollar sign $ 💸 — that one triggers variable expansion, same as we talked about above. Also the backquote (grave accent) ` (which doesn't mean anything special yet, ok don't panic) and the reverse solidus \. The \ will escape any of these: dollar sign $ (so variable expansion doesn't happen), backquote (grave accent) `, double-quote " (so you don't accidentally end the quote), and reverse solidus \ (so you don't escape by accident, i.e. so you can embed a reverse solidus character as-is). Other than that it has no special meaning. Periodt.
Arguments enclosed in $'dollar-single-quotes' are basically normal single quotes with the DLC installed ✨ — reverse solidus escape sequences get expanded like this:
- \a — bell control character (ASCII and ISO-10646 BEL) 🔔
- \b — backspace control character (ASCII and ISO-10646 BS)
- \E — escape control character (ASCII and ISO-10646 ESC)
- \e — the same ✨
- \f — form feed control character (ASCII and ISO-10646 FF)
- \n — line feed control character (ASCII and ISO-10646 LF)
- \r — carriage return control character (ASCII and ISO-10646 CR)
- \t — horizontal tabulator control character (ASCII and ISO-10646 HT)
- \v — vertical tabulator control character (ASCII and ISO-10646 VT)
- \\ — emits a reverse solidus character
- \' — single quote
- \" — double quote (the escaping is optional, do with that what u will)
- \NNN — eight-bit byte with the octal value NNN (one to three octal digits), optionally prefixed by an additional 0. A 0 byte will suppress further output for the quoted argument 💀
- \xHH — eight-bit byte with the hexadecimal value HH (one or two hexadecimal characters, no prefix, see vexpr). A 0 byte will suppress further output for the quoted argument 💀
- \UHHHHHHHH — the Unicode / ISO-10646 character with the hexadecimal codepoint value HHHHHHHH (one to eight hexadecimal characters) — note that Unicode defines the maximum codepoint ever to be supported as 0x10FFFF (in planes of 0xFFFF characters each). This escape is only supported in locales that support Unicode (see “Character sets”), in other cases the sequence will remain unexpanded unless the given code point is ASCII compatible or (if the [Option]al character set conversion is available) can be represented in the current locale. The character NUL will suppress further output for the quoted argument.
- \uHHHH — identical to \UHHHHHHHH except it takes only one to four hexadecimal characters.
- \cX — emits the non-printable (ASCII and compatible) C0 control codes 0 (NUL) to 31 (US), and 127 (DEL). Printable representations of ASCII control codes can be created by mapping them to a different, visible part of the ASCII character set. Adding the number 64 achieves this for the codes 0 to 31, here 7 (BEL): 7 + 64 = 71 = G. The real operation is a bitwise logical XOR with 64 (bit 7 set, see vexpr), thus also covering code 127 (DEL), which is mapped to 63 (question mark): ? vexpr ^ 127 64.

Whereas historically circumflex notation has often been used for visualization purposes of control codes, as in ^G, the reverse solidus notation has been standardized: \cG. Some control codes also have standardized (ISO-10646, ISO C) aliases, as shown above (\a, \n, \t etc) : whenever such an alias exists it will be used for display purposes. The control code NUL (\c@, a non-standard extension) will suppress further output for the remains of the token (which may extend beyond the current quote), or, depending on the context, the remains of all arguments for the current command. cute but also terrifying 🫶

\$NAME — non-standard extension 🎀 expands the given variable name, as above. Brace enclosing the name is supported.
\`{command} — not yet supported, just to raise awareness: non-standard extension. (Manifesting this one for later iykyk 🙈)

💀 Caveats 💀

Bestie these are the receipts, look closely:

? echo 'Quotes '${HOME}' and 'tokens" differ!"# no comment
? echo Quotes ${HOME} and tokens differ! # comment
? echo Don"'"t you worry$'\x21' The sun shines on us. $'\u263A'

💬 Message list arguments 💬

So many commands operate on message list specifications, as documented in “Specifying messages”. Here's the tea ☕ — the argument input is first split into individual tokens via “Shell-style argument quoting”, and those are then interpreted as the mentioned specifications.

If no explicit message list has been specified, many commands will search for and use the next message forward that satisfies the commands' requirements, and if there are no messages forward of the current message, the search proceeds backwards 🔄; if there are no good messages at all to be found, an error message is shown and the command is aborted. No cap.

The verbose output of the command list will indicate whether a command searches for a default message, or not 👀

🧬 Raw data arguments for codec commands 🧬

Okay so there's this special set of commands, and they all have the string “codec” in their name, like addrcodec, shcodec, urlcodec — they take raw string data as input, which literally means the content of the command input line is passed completely unexpanded and otherwise unchanged 🙅‍♀️. Like this the effect of the actual codec is visible without any noise of possible shell quoting rules etc., i.e. the user can input one-to-one the desired or questionable data 😭

To gain a level of expansion, the entire command line can be evaluated first, for example:

? vput shcodec res encode /usr/Schönes Wetter/heute.txt
? echo $res
$'/usr/Sch\u00F6nes Wetter/heute.txt'
? shcodec d $res
$'/usr/Sch\u00F6nes Wetter/heute.txt'
? eval shcodec d $res
/usr/Schönes Wetter/heute.txt

See the difference? eval said "let me handle that" and it ate 💅

📁 Filename transformations 📁

Filenames, where expected, and unless documented otherwise, are subsequently subject to the following filename transformations, in sequence ⭐:

If the given name is a registered shortcut, it will be replaced with the expanded shortcut. This step is mostly taken for folders only 📂
The filename is matched against the following patterns or strings. But for plus +file folder expansion this step is mostly taken for folders only.
- # — (Number sign) is expanded to the previous file ⏪
- % — (Percent sign) is replaced by the invoking user's primary system mailbox, which either is the (itself expandable) inbox if that is set, the standardized absolute pathname indicated by MAIL if that is set, or a built-in compile-time default otherwise. When opening a folder the used name is actively checked for being a primary mailbox, first against inbox, then against MAIL 📬
- %user — expands to the primary system mailbox of user (and never the value of inbox, regardless of its actual setting).
- & — (Ampersand) is replaced with the invoking user's secondary mailbox, the MBOX 🗄️
- +file — refers to a file in the folder directory (if that variable is set) 📁
- %:filespec — expands to the same value as filespec, but has special meaning when used with, for example, the command folder: the file will be treated as a primary system mailbox by, among others, the mbox and save commands, meaning that messages that have been read in the current session will be moved to the MBOX mailbox instead of simply being flagged as read 👑
Meta expansions may be applied to the resulting filename, as allowed by the operation and applicable to the resulting access protocol (also see “On URL syntax and credential lookup”). For the file-protocol, a leading tilde ~ character will be replaced by the expansion of HOME, except when followed by a valid user name, in which case the home directory of the given user is used instead 🏠

A shell expansion as if specified in double-quotes (see “Shell-style argument quoting”) may be applied, so that any occurrence of $VARIABLE (or ${VARIABLE}) will be replaced by the expansion of the variable, if possible; “INTERNAL VARIABLES” as well as “ENVIRONMENT” (shell) variables can be accessed through this mechanism 💖

Shell pathname wildcard pattern expansions (glob(7)) may be applied as documented. If the fully expanded filename results in multiple pathnames and the command is expecting only one file, an error results 🚨

In interactive context, in order to allow simple value acceptance (via “ENTER”), arguments will usually be displayed in a properly quoted form, so a file diet\ is \curd.txt may be displayed as 'diet\ is \curd.txt'. Lowkey so considerate 🥺

👑 Commands 👑

The following commands are available:

`!` 💥

Okay so ! executes the SHELL command that follows it, replacing unescaped exclamation marks with the previously executed command if the internal variable bang is set. This command supports vput as documented in “Command modifiers”, and it manages the error number !. A 0 or positive exit status ? reflects the exit status of the command; negative ones mean an error happened before the command was executed, or that the program did not exit cleanly, but maybe due to a signal: the error number is ^ERR-CHILD then.

When you pair it with the vput modifier, these special cases exist: a negative exit status happens if the collected data could not be stored in the given variable, which is a ^ERR-NOTSUP error that should otherwise not occur. ^ERR-CANCELED means no temporary file could be created to collect the command output at first glance. In catchable out-of-memory situations ^ERR-NOMEM will occur and S-nail will try to store the empty string, just like with all other detected error conditions.

`#` 🎀

The comment-command causes the entire line to be ignored. Note: this really is a normal command whose purpose is to discard its arguments, not a “comment-start” special character — which means that, for example, trailing comments on a line are not possible (except for commands which use “Shell-style argument quoting”).

`+` 🌈

Goes to the next message in sequence and types it (like “ENTER”).

`-` 🦋

Display the preceding message, or the n'th previous message if given a numeric argument n.

`=` 💅

Shows the message number of the current message (the “dot”) when used without arguments, that of the given list otherwise. Output numbers will be separated from each other with the first character of ifs, and followed by the first character of if-ws, if that is not empty and not identical to the first. If that results in no separation at all, a space character is used. This command supports vput (see “Command modifiers”), and manages the error number !.

`?` ✨

[Option] Show a brief summary of commands. [Option] Given an argument, a synopsis for the command in question is shown instead; commands can be abbreviated in general and this command can be used to see the full expansion of an abbreviation including the synopsis — try, for example, ?h, ?hel and ?help and see how the output changes. To avoid aliases being resolved, the modifier \ can be prepended to the argument, but note it must be quoted. This mode also supports a more verbose output, which will provide the information documented for list.

`|` 🫶

A synonym for the pipe command.

`account`, `unaccount` (`ac`, `una`) 🧾

(ac, una) Creates, selects or lists (an) account(s). Accounts are special incarnations of defined macros and group commands and variable settings which together usually arrange the environment for the purpose of creating an email account. Different to normal macros settings which are covered by localopts — here by default enabled! — settings will not be reverted before the account is changed again. The special account null (case-insensitive) always exists, and all but it can be deleted by the latter command, and in one operation with the special name *. Also for all but it a possibly set on-account-cleanup hook is called once they are left, also for program exit.

Without arguments a listing of all defined accounts is shown. With one argument the given account is activated: the system inbox of that account will be activated (as via folder), a possibly installed folder-hook will be run, and the internal variable account will be updated. The two argument form behaves identical to defining a macro as via define. Important settings for accounts include folder, from, hostname, inbox, mta, password and user (“On URL syntax and credential lookup”), as well as things like tls-config-pairs (“Encrypted network communication”), and protocol specifics like imap-auth, pop3-auth, smtp-auth.

account myisp {
  set folder=~/mail inbox=+syste.mbox record=+sent.mbox
  set from='(My Name) myname@myisp.example'
  set mta=smtp://mylogin@smtp.myisp.example
}

`addrcodec` 🧚

Perform email address codec transformations on the raw-data argument, rather according to email standards (RFC 5322; [v15 behaviour may differ] will furtherly improve). Supports vput (see “Command modifiers”), and manages the error number !. The first argument must be either [+[+[+]]]e[ncode], d[ecode], s[kin] or skinl[ist] and specifies the operation to perform on the rest of the line.

Decoding will show how a standard-compliant MUA will display the given argument, which should be an email address. Please be aware that most MUAs have difficulties with the address standards, and vary wildly when (comments) in parenthesis, “double-quoted” strings, or quoted-pairs, as below, become involved. [v15 behaviour may differ] S-nail currently does not perform decoding when displaying addresses.

Skinning is identical to decoding but only outputs the plain address, without any string, comment etc. components. Another difference is that it may fail with the error number ! set to ^ERR-INVAL if decoding fails to find a(n) (valid) email address, in which case the unmodified input will be output again.

skinlist first performs a skin operation, and thereafter checks a valid address for whether it is a registered mailing list (see mlist and mlsubscribe), eventually reporting that state in the error number ! as ^ERR-EXIST. (This state could later become overwritten by an I/O error, though.)

Encoding supports four different modes; lesser automated versions can be chosen by prefixing one, two or three plus signs: the standard imposes a special meaning on some characters, which thus have to be transformed to so-called quoted-pairs by pairing them with a reverse solidus \ in order to remove the special meaning; this might change interpretation of the entire argument from what has been desired, however! Specify one plus sign to remark that parenthesis shall be left alone, two for not turning double quotation marks into quoted-pairs, and three for also leaving any user-specified reverse solidus alone. The result will always be valid, if a successful exit status is reported ([v15 behaviour may differ] the current parser fails this assertion for some constructs). [v15 behaviour may differ] Addresses need to be specified in between angle brackets <, > if the construct becomes more difficult, otherwise the current parser will fail; it is not smart enough to guess right.

? addrc enc "Hey, you",<diet@exam.ple>\ out\ there
"\"Hey, you\", \\ out\\ there" <diet@exam.ple>
? addrc d "\"Hey, you\", \\ out\\ there" <diet@exam.ple>
"Hey, you", \ out\ there <diet@exam.ple>
? addrc s "\"Hey, you\", \\ out\\ there" <diet@exam.ple>
diet@exam.ple

`alias`, `unalias` (`a`, `una`) 💌

[Only new quoting rules] (a, una) Define or list, and remove, respectively, address aliases — which are a method of creating personal distribution lists that map a single name to none to multiple receivers, to be expanded after “Compose mode” is left; the expansion correlates with metoo. The latter command removes all given aliases, and the special name asterisk * will remove all existing aliases. When used without arguments the former shows a list of all currently known aliases, with one argument only the target(s) of the given one. When given two arguments, hyphen-minus - being the first, the target(s) of the second is/are expanded recursively.

In all other cases the given alias is newly defined, or will be appended to: arguments must either be themselves valid alias names, or any other address type (see “On sending mail, and non-interactive mode”). Recursive expansion of aliases can be prevented by prefixing the desired argument with the modifier reverse solidus \. A valid alias name conforms to mta-aliases syntax, but follow-up characters can also be the number sign #, colon :, commercial at @, exclamation mark !, period . as well as “any character that has the high bit set”. The dollar sign $ may be the last character. The number sign # may need “Shell-style argument quoting”.

[v15 behaviour may differ] Unfortunately the colon is currently not supported, as it interferes with normal address parsing rules. [v15 behaviour may differ] Such high bit characters will likely cause warnings at the moment for the same reasons why colon is unsupported; also, in the future locale dependent character set validity checks will be performed.

? alias cohorts  bill jkf mark kridle@ucbcory ~/cohorts.mbox
? alias mark  mark@exam.ple
? set mta-aliases=/etc/aliases

`alternates`, `unalternates`

[Only new quoting rules] — also known by its little nickname (alt) 💅 — this pair manages your list of alternate addresses or names for the active user. Any member of that list gets removed from recipient lists (except one, bestie, we keep exactly one 🫶).

There's also a set of implicit alternates that just… exists, formed from the values of LOGNAME, from, sender and reply-to. Note that from will not be used if sender is set. Slay.

unalternates is the deleter: it removes the given list of alternates, and * is the special name that discards all existing alternate names. Periodt.

alternates itself manages the error number !. When you run it with no arguments it shows the current set of alternates — and in this mode only, it also supports vput (see “Command modifiers”). Otherwise the arguments you give it (after being checked for validity, obviously) get appended to the list of alternate names; in posix mode they replace that list instead. 🔥

`answered`, `unanswered`

Takes a message list and marks each message as (not) having been answered — it's giving "seen ✅ / not seen 🙈". Messages get marked answered automatically when they're replyd to, but only if the markanswered variable is set. See the section “Message states”. ✨

`bind`, `unbind`

[Option] [Only new quoting rules] — okay so this is the fun one 👑

bind extends the MLE (see “On terminal control and line editor”) with freely configurable key bindings. unbind removes, from the given context, the given key binding — and both of those can be specified as the wildcard *, so unbind * * will remove all bindings of all contexts. Iconic.

Heads up 🫶: due to initialization order, unbinding will not work for built-in key bindings upon program startup. Please use line-editor-no-defaults for this purpose instead. No cap.

With zero arguments, or with a context name, bind shows all key bindings (of that given context — an asterisk * will iterate over all contexts). You get a more verbose listing if either debug or verbose are set.

With two or more arguments, a specific binding is shown, or (re)established:

the first argument is the context to which the binding shall apply
the second argument is a comma-separated list of the “keys” which form the binding
further arguments get joined to form the expansion, and cause the binding to be created or updated

To say "don't auto-commit this one, let the user keep editing the expansion", you place a commercial at @ — which gets removed — last in the expansion; leading and trailing whitespace is finally removed from it. Reverse solidus can't be the last character of the expansion, and an empty expansion will be rejected. 🚫

Contexts define when a binding applies, i.e. a binding won't be seen unless the context it's defined for is currently active. This is not true for the shared binding base, which is the foundation for all other bindings and as such always applies — its bindings, however, only apply secondarily. The available contexts are:

the shared base
the default context, used in all not otherwise documented situations
compose, which applies only to “Compose mode”

Bindings are specified as a comma-separated list of byte-sequences, where each list entry corresponds to one “key” (press). 🎹 Byte sequence boundaries get forcefully terminated after bind-inter-byte-timeout milliseconds, whereas key sequences can be timed out via bind-inter-key-timeout. A list entry may also refer to the name of a terminal capability, indicated by a leading colon character : — several dozen names are compiled in and may be specified either by their terminfo(5) name, or, if existing, by their termcap(5) name, regardless of the actually used *[Option]*al terminal control library. But literally any capability may be used, as long as the name is resolvable by the *[Option]*al control library, or was defined via the internal variable termcap.

Input sequences are not case-normalized — an exact match is required to update or remove a binding. It's advisable to use an initial escape or other control character (like '\cA') for user (as opposed to purely terminal capability based) bindings, so you avoid ambiguities; it also reduces search time. 🕵️‍♀️ Examples:

? bind base a,b echo one
? bind base $'\E',d mle-snarf-word-fwd # Esc(ape)
? bind base $'\E',$'\c?' mle-snarf-word-bwd # Esc,Delete
? bind default $'\cA',:khome,w 'echo Editable binding@'
? bind default a,b,c rm -irf / @  # Also editable
? bind default :kf1 File %
? bind compose :kf1 ~v

Note that the entire comma-separated list is first parsed (over) as a shell-token with whitespace as the field separator, and then parsed and expanded for real with comma as the field separator — so whitespace needs to be properly quoted, see “Shell-style argument quoting”. 😭

Also: using Unicode reverse solidus escape sequences renders a binding defunctional if the locale doesn't support Unicode (see “Character sets”), and using terminal capabilities does the same if no (corresponding) terminal control support is (currently) available. And adding, deleting or modifying a key binding invalidates the internal prebuilt lookup tree — it gets recreated as necessary, and this process is visualized in most verbose as well as in debug mode. 🌈

The following terminal capability names are built-in and can be used in terminfo(5) or (if available) the two-letter termcap(5) notation. See the respective manual for a list of capabilities. The program infocmp(1) can be used to show all the capabilities of TERM or the given terminal type; using the -x flag will also show supported (non-standard) extensions. 🔍

kbs or kb — Backspace.
kdch1 or kD — Delete character.
kDC or *4 — shifted variant.
kel or kE — Clear to end of line.
kext or @9 — Exit.
kich1 or kI — Insert character.
kIC or #3 — shifted variant.
khome or kh — Home.
kHOM or #2 — shifted variant.
kend or @7 — End.
knp or kN — Next page.
kpp or kP — Previous page.
kcub1 or kl — Left cursor (with more modifiers: see below).
kLFT or #4 — shifted variant.
kcuf1 or kr — Right cursor (ditto).
kRIT or %i — shifted variant.
kcud1 or kd — Down cursor (ditto).
kDN — shifted variant (only terminfo).
kcuu1 or ku — Up cursor (ditto).
kUP — shifted variant (only terminfo).
kf0 or k0 — Function key 0. Add one for each function key up to kf9 and k9, respectively.
kf10 or k; — Function key 10.
kf11 or F1 — Function key 11. Add one for each function key up to kf19 and F9, respectively.

Some terminals support key-modifier combination extensions, e.g. Alt+Shift+xy. 💫 For example, the delete key kdch1: in its shifted variant the name is mutated to kDC, then a number is appended for the states Alt (kDC3), Shift+Alt (kDC4), Control (kDC5), Shift+Control (kDC6), Alt+Control (kDC7), and finally Shift+Alt+Control (kDC8). Same deal for the left cursor key kcub1: KLFT, KLFT3, KLFT4, KLFT5, KLFT6, KLFT7, KLFT8. 🤯

`call`

[Only new quoting rules] — calls the given macro, which must have been created via define (see there for more), otherwise an ^ERR-NOENT error occurs. 💀

Real talk: calling macros recursively will at some point excess the stack size limit, causing a hard program abortion. If recursively calling a macro is the last command of the current macro, consider using the command xcall instead — it first releases all resources of the current macro before replacing the current macro with the called one. 🙏

`call_if`

Identical to call if the given macro has been created via define, but it does not fail nor warn if the macro doesn't exist. It's the chill, no-drama version. 🦋

`cd`

Synonym for chdir. That's it, that's the whole vibe. 💜

`certsave`

[Option] — only applicable to S/MIME signed messages. Takes an optional message list and a filename, and saves the certificates contained within the message signatures to the named file in both human-readable and PEM format. 🔐

Later you can use those certificates to send encrypted messages to the respective message senders by setting smime-encrypt-USER@HOST variables. Main character cryptography energy. 👑

`charsetalias`, `uncharsetalias`

[Only new quoting rules] — manages alias mappings for (conversion of) “Character sets”. 🌸

Alias processing is not performed for “INTERNAL VARIABLES”, for example charset-8bit, and mappings are ineffective if character set conversion is not available (features does not announce ,+iconv,). Expansion happens recursively for cases where aliases point to other aliases (built-in loop limit: 8). 🔁

uncharsetalias deletes all aliases given as arguments, or all at once when given the asterisk *.

charsetalias shows the list of all currently defined aliases if used without arguments, or the target of the given single argument. When given two arguments with hyphen-minus - being the first, the second is instead expanded recursively. In all other cases the given arguments are treated as pairs of character sets and their desired target alias name, creating new or updating already existing aliases. ✨

`chdir`

[Only new quoting rules] (ch) — change the working directory to HOME or the given argument. Also a synonym for cd. 🏠

`collapse`, `uncollapse`

Okay so these two? Only make sense when you're in threaded sort mode, bestie — like, don't even try otherwise. collapse takes a message list and makes every reply to those messages invisible in header summaries… except for new messages and the “dot” 🎀. And here's the cute bit: when a message whose replies are collapsed actually gets displayed, all of those replies are automatically uncollapsed for you. Very demure, very mindful.

uncollapse is just the undo button. It undoes collapsing. That's the whole vibe 💅

`colour`, `uncolour`

[Option][Only new quoting rules] — Manage colour mappings of and for a “Coloured display” ✨

With no arguments at all, colour shows you every currently defined mapping. Slay. Otherwise it's expecting a colour type (case-insensitive, obviously), and it's gotta be one of these:

256 — for 256-colour terminals 🌈
8, ansi or iso — for the standard 8-colour ANSI / ISO 6429 colour palette
1 or mono — for monochrome terminals, which only support (some) font attributes 😭

And if you give it the type with no further arguments, it shows the list of all currently defined mappings of that type — and heads up, the special all or * also show all currently defined mappings 👑

Otherwise, bestie, here's the lineup: the second argument defines the mappable slot, the third argument is a (comma-separated list of) colour and font attribute specification(s), and the optionally supported fourth argument can be used to specify a precondition. If conditioned mappings exist they get tested in (creation) order unless a (case-insensitive) match has been found — and the default mapping (if any has been established) will only be chosen as a last resort. No cap.

The types of available preconditions depend on the mappable slot, and the following ones exist:

`mle-` mappings

Mappings prefixed with mle- are used for the [Option]al built-in Mailx-Line-Editor (MLE, see “On terminal control and line editor”) and they do not support preconditions. Sorry babes.

mle-position — this mapping is used for the position indicator that's visible when a line can't be fully displayed on the screen.
mle-prompt — used for the prompt 💖
mle-error — used for the occasionally appearing error indicator that gets joined onto the prompt. [v15 behaviour may differ] Also used for error messages written on standard error.

`sum-` mappings

Mappings prefixed with sum- are used in header summaries, and they all understand the preconditions dot (the current message) and older for elder messages (only honoured in conjunction with datefield-markout-older).

sum-dotmark — this mapping is used for the “dotmark” that can be created with the %> or %< formats of the variable headline.
sum-header — for the complete header summary line except the “dotmark” and the thread structure.
sum-thread — for the thread structure, which can be created with the %i format of the variable headline.

`view-` mappings

Mappings prefixed with view- are used when displaying messages 🦋

view-from_ — this mapping is used for so-called From_ lines, which are MBOX file format specific header lines (also see mbox-rfc4155).
view-header — for header lines. A comma-separated list of headers to which the mapping applies may be given as a precondition; if the [Option]al regular expression support is available then if any of the “magic regular expression characters” is seen the precondition will be evaluated as (an extended) one. Iykyk 🧚
view-msginfo — for the introductional message info line.
view-partinfo — for MIME part info lines.

colour definitions & font attributes

The following (case-insensitive) colour definitions and font attributes are understood, and you can specify multiple of them in a comma-separated list:

ft= — a font attribute: bold, reverse or underline. It is possible (and often applicable) to specify multiple font attributes for a single mapping 💅
fg= — foreground colour attribute, in order (numbers 0 - 7): black, red, green, brown, blue, magenta, cyan or white. To specify a 256-colour mode a decimal number colour specification in the range 0 to 255, inclusive, is supported, and interpreted as follows:
- 0 - 7 — the standard ISO 6429 colours, as above.
- 8 - 15 — high intensity variants of the standard colours.
- 16 - 231 — 216 colours in tuples of 6.
- 232 - 255 — grayscale from black to white in 24 steps.

And here's the little script to preview all of it, literally copy-paste this, it's giving main character energy:

#!/bin/sh -
fg() { printf "\033[38;5;${1}m($1)"; }
bg() { printf "\033[48;5;${1}m($1)"; }
i=0
while [ $i -lt 256 ]; do fg $i; i=$(($i + 1)); done
printf "\033[0m\n"
i=0
while [ $i -lt 256 ]; do bg $i; i=$(($i + 1)); done
printf "\033[0m\n"

bg= — background colour attribute (see fg= for possible values).

Now uncolour — this one will remove, for the given colour type (the special type * selects all), the given mapping. If the optional precondition argument is given, only the exact tuple of mapping and precondition is removed. The special name * will remove all mappings (no precondition allowed), thus uncolour * * will remove all established mappings 💀

`commandalias`, `uncommandalias`

[Only new quoting rules] — Define or list, and remove, respectively, command aliases 🌸

An (command)alias can be used everywhere a normal command can be used, but it always takes precedence: any arguments that are given to the command alias are joined onto the alias expansion, and the resulting string forms the command line that is, in effect, executed. Iconic behaviour honestly.

uncommandalias removes all given aliases — and the special name asterisk * will remove all existing aliases.

When commandalias is used without arguments, it shows a list of all currently known aliases; with one argument only, it shows the expansion of the given one.

With two or more arguments a command alias is defined or updated: the first argument is the name under which the remaining command line should be accessible, and the content of that can be just about anything. An alias may itself expand to another alias, but to avoid expansion loops further expansion will be prevented if an alias refers to itself or if an expansion depth limit is reached 🫶 Explicit expansion prevention is available via reverse solidus \, one of the “Command modifiers”.

? commandalias xx
s-nail: `commandalias': no such alias: xx
? commandalias xx echo hello,
? commandalias xx
commandalias xx 'echo hello,'
? xx
hello,
? xx world
hello, world

`Copy`

(C) — Similar to copy, but copy the messages to a file named after the local part of the sender of the first message instead of taking a filename argument; outfolder is inspected to decide on the actual storage location 🎀

`copy`

(c) — Copy messages to the named file and do not mark them as being saved; otherwise identical to save. Literally the chill version of save.

`csop`

[Only new quoting rules] — A multiplexer command which provides C-style string operations on 8-bit bytes without a notion of locale settings and character sets, effectively assuming ASCII data. For numeric and other operations refer to vexpr ✨ vput, one of the “Command modifiers”, is supported.

The error result is -1 for usage errors and numeric results, the empty string otherwise; missing data errors, as for unsuccessful searches, result in the ! error number being set to ^ERR-NODATA.

Where the question mark ? modifier suffix is supported, a case-insensitive (ASCII mapping) operation mode is supported; the keyword case is optional so that find? and find?case are identical 👑

length — Queries the length of the given argument.
hash, hash32 — Calculates a hash value of the given argument. The latter will return a 32-bit result regardless of host environment. ? modifier suffix is supported. These use Chris Torek's hash algorithm, the resulting hash value is bit mixed as shown by Bret Mulvey.
find — Search for the second in the first argument. Shows the resulting 0-based offset shall it have been found. ? modifier suffix is supported.
substring — Creates a substring of its first argument. The optional second argument is the 0-based starting offset, a negative one counts from the end; the optional third argument specifies the length of the desired result, a negative length leaves off the given number of bytes at the end of the original string; by default the entire string is used. This operation tries to work around faulty arguments (set verbose for error logs), but reports them via the error number ! as ^ERR-OVERFLOW 😭
trim — Trim away whitespace characters from both ends of the argument.
trim-front — Trim away whitespace characters from the begin of the argument.
trim-end — Trim away whitespace characters from the end of the argument.
cwd — tells you the current working directory, exactly like getcwd(3) reports it ✨. Supports vput (peep “Command modifiers”) and the return status is tracked via ?. iykyk 💅
Decrypt [Option] — for unencrypted messages this is literally identical to Copy; encrypted messages get decrypted first (if possible, bestie) and then copied 🎀
decrypt [Option] — same energy as above but lowercase: for unencrypted messages it's identical to copy, and encrypted ones get decrypted first if possible, then copied 💖
define, undefine — the second one nukes the given macro, and the special name * discards all existing macros 🗑️. Deletion of macro(s) can happen from within running macro(s), including self-deletion (main character energy fr). Without arguments, define prints the current list of macros including their content; otherwise it defines a macro, replacing an existing one of the same name where applicable ✨

A defined macro can be invoked explicitly with the call, call_if and xcall commands, or implicitly when a macro hook fires, like a folder-hook 🪝. You can stop execution of a macro body from inside by calling return.

Temporary macro block-scope variables can be created or deleted with the local command modifier together with set and unset respectively. To force unrolling of changes made to (global) “INTERNAL VARIABLES”, use the localopts command instead; its covered scope depends on how (i.e. “as what”: normal macro, folder hook, hook, account switch) the macro is invoked.

Inside a called macro, the given positional parameters are implicitly local to the macro's scope, and can be accessed via the variables *, @, # and 1 and any other positive unsigned decimal number less than or equal to #. Positional parameters can be shifted, or completely replaced, removed, etc. via vpospar. A helpful command for numeric computation and string evaluations is vexpr, and csop offers C-style byte string operations 💅

define name {
  command1
  command2
  ...
  commandN
}

define exmac {
  echo Parameter 1 of ${#} is ${1}, all: ${*} / ${@}
  return 1000 0
}
call exmac Hello macro exmac!
echo ${?}/${!}/${^ERRNAME}

delete, undelete — (d, u) marks the given message list as being / not being ‘deleted’ respectively 🌸. If no argument is specified, the usual search for a visible message happens, as documented for “Message list arguments”, showing only the next input prompt if the search fails. Deleted messages will neither be saved in the “secondary mailbox” MBOX nor be available for most other commands, no cap 😭. If the autoprint variable is set, the new “dot” or the last message restored (respectively) is automatically typed; also see dp, dt.
digmsg [Only new quoting rules] — digging (information out of) messages is possible through digmsg objects, which can be created for the given message number 🕵️‍♀️. In “Compose mode” the hyphen-minus - will instead open the message that's being composed. If a hyphen-minus is given as the optional third argument, output goes to the standard output channel instead of being consumed by the readsh command (better here than read or readall) ✨

Objects can be removed again by giving the same identifier used for creation; you could skip this step — objects get automatically closed when the active folder (mailbox) or compose mode is left, respectively 👑. In all other use cases the second argument is an object identifier, and the third and all following arguments are interpreted as via ~^ (see “COMMAND ESCAPES”):

? vput = msgno; digmsg create $msgno
? digmsg $msgno header list;   readall x;   echon $x
210 Subject From To Message-ID References In-Reply-To
? digmsg $msgno header show Subject;readall x;echon $x
212 Subject
'Hello, world'

? digmsg remove $msgno

discard — (di) identical to ignore. Superseded by the multiplexer headerpick 💀
dp, dt — delete the given messages and automatically type the new “dot” if one exists, regardless of what autoprint is set to 🔥
dotmove — moves the “dot” up or down by one message when given a + or - argument respectively 🦋
draft, undraft — take message lists and mark each given message as being draft, or not being draft, respectively, as documented in the section “Message states” 🎀
echo [Only new quoting rules]``(ec) — prints the given strings, equivalent to the shell utility echo(1), that is, “Shell-style argument quoting” expansion is performed and — unlike the otherwise identical echon — a trailing newline is echoed 💖. vput as documented in “Command modifiers” is supported, and the error number ! is managed: if data is stored in a variable then the return value reflects the length of the result string on success and is -1 on error.

Remarks: this command traditionally (in BSD Mail) also performed “Filename transformations”, which is standard incompatible and hard to handle because quoting transformation patterns is not possible 😬; the subcommand file-expand of vexpr can be used to expand filenames.

echoerr [Only new quoting rules] — identical to echo, but the message is written to standard error and prefixed by log-prefix. Also see echoerrn. In interactive sessions, the [Option]al message ring queue for errors will be used instead, if available and vput was not used 🌈
echon [Only new quoting rules] — identical to echo, but it doesn't write or store a trailing newline ✨
echoerrn [Only new quoting rules] — identical to echoerr, but doesn't write or store a trailing newline 🌸
edit — (e) point the text EDITOR at each message from the given list in turn ✏️. Modified contents are discarded unless the writebackedited variable is set, and they're not used unless the mailbox can be written to and the editor returns a successful exit status 😭. visual can be used instead for a more display-oriented editor.
elif — part of the if (see there for more), elif, else, endif conditional — if the condition of a preceding if was false, check the following condition and execute the following block if it evaluates true 💅
else — (el) part of the if (see there for more), elif, else, endif conditional — if none of the conditions of the preceding if and elif commands was true, the else block is executed 🫶
endif — (en) marks the end of an if (see there for more), elif, else, endif conditional execution block ⭐
environ [Only new quoting rules] — there's a strict separation between “INTERNAL VARIABLES” and the program “ENVIRONMENT”, which is inherited by child processes 👑. Some variables of the latter are however vivid for program operation, their purpose is known, therefore they've been integrated transparently into handling of the former, as accessible via set and unset. To integrate any other environment variable, and/or to export internal variables into the process environment where they normally aren't, a link needs to become established with this command, for example

environ link PERL5LIB TZ

Afterwards, changing such variables with set will cause automatic updates of the environment too ✨. Sufficient system support provided (it was in BSD as early as 1987, and is standardized since Y2K), removing such variables with unset will remove them from the environment as well, but in any case the knowledge that they ever have been linked will be lost 😭. This implies that localopts may cause loss of such links.

The subcommand unlink removes an existing link without otherwise touching variables; the set and unset subcommands are identical to set and unset, but additionally update the program environment accordingly; removing a variable breaks any freely established link 💀

errors [Option] — since console user interfaces at times scroll error messages by too fast and/or out of scope, data can additionally be sent to an error queue manageable by this command 📋: show or no argument will display and clear the queue, clear will only clear it. As the queue becomes filled with errors-limit entries, the eldest entries are dropped. There are also the variables ^ERRQUEUE-COUNT and ^ERRQUEUE-EXISTS 🦋
eval [Only new quoting rules] — construct a command by concatenating the arguments, separated with a single space character, and then evaluate the result 🔥. This command passes through the exit status ? and error number ! of the evaluated command; also see call.

define xxx {
  echo "xxx arg <$1>"
  shift
  if $# -gt 0
    \xcall xxx "$@"
  endif
}
define yyy {
  eval "$@ ' ball"
}
call yyy '\call xxx' "b\$'\t'u ' "
call xxx arg <b      u>
call xxx arg <  >
call xxx arg <ball>

`exit` (aka `ex` or `x`)

okay so bestie, exit is the bail-out button 💅 — it exits from S-nail without changing the active mailbox and skips any saving of messages in the “secondary mailbox” MBOX, as well as a possibly tracked line editor history-file. A possibly set on-account-cleanup will be invoked, however. The optional status number argument will be passed through to exit(3). [v15 behaviour may differ] For now it can happen that the given status will be overwritten, later this will only occur if a later error needs to be reported onto an otherwise success indicating status.

`File` (aka `Fi`)

Like folder, but open the mailbox read-only. That’s the whole vibe — same energy, no writing back. 🎀

`file` (aka `fi`)

See folder. no cap, that’s literally the whole entry.

`filetype`, `unfiletype`

Only new quoting rules ✨ Define, list, and remove, respectively, file handler hooks — these provide (shell) commands that enable S-nail to load and save MBOX files from and to files with the registered file extensions, as shown and described for folder. The extensions are used case-insensitively, yet the auto-completion feature of for example folder will only work case-sensitively. An intermediate temporary file will be used to store the expanded data. The latter command will remove hooks for all given extensions, asterisk * will remove all existing handlers.

When used without arguments the former shows a list of all currently defined file hooks, with one argument the expansion of the given alias. Otherwise three arguments are expected, the first specifying the file extension for which the hook is meant, and the second and third defining the load- and save commands to deal with the file type, respectively, both of which must read from standard input and write to standard output. Changing hooks will not affect already opened mailboxes ([v15 behaviour may differ] except below). [v15 behaviour may differ] For now too much work is done, and files are oftened read in twice where once would be sufficient: this can cause problems if a filetype is changed while such a file is opened; this was already so with the built-in support of .gz etc. in Heirloom, and will vanish in v15. [v15 behaviour may differ] For now all handler strings are passed to the SHELL for evaluation purposes; in the future a ! prefix to load and save commands may mean to bypass this shell instance: placing a leading space will avoid any possible misinterpretations.

? filetype bz2 'bzip2 -dc' 'bzip2 -zc' \
    gz 'gzip -dc' 'gzip -c'  xz 'xz -dc' 'xz -zc' \
    zst 'zstd -dc' 'zstd -19 -zc' \
    zst.pgp 'gpg -d | zstd -dc' 'zstd -19 -zc | gpg -e'
? set record=+sent.zst.pgp

`flag`, `unflag`

Take message lists and mark the messages as being flagged, or not being flagged, respectively, for urgent/special attention 🌸 See the section “Message states”.

`Folder` (aka `Fold`)

Like folder, but open the mailbox read-only. Same icon energy as File, just with the folder spelling. 🫶

`folder` (aka `fold`)

Open a new, or show status information of the current mailbox. If an argument is given, changes (such as deletions) will be written out, a new mailbox will be opened, the internal variables mailbox-resolved and mailbox-display will be updated, a set according folder-hook is executed, and optionally a summary of headers is displayed if the variable header is set.

“Filename transformations” will be applied to the name argument, and protocol:// prefixes are, i.e., URL (see “On URL syntax and credential lookup”) syntax is understood, as in mbox:///tmp/somefolder. If a protocol prefix is used the mailbox type is fixated, otherwise opening none-existing folders uses the protocol defined in newfolders.

For the protocols mbox and file (MBOX database), as well as eml (electronic mail message [v15 behaviour may differ] read-only) the list of all registered filetypes is traversed to check whether hooks shall be used to load (and save) data from (and to) the given name. Changing hooks will not affect already opened mailboxes. For example, the following creates hooks for the gzip(1) compression tool and a combined compressed and encrypted format:

? filetype \
    gzip 'gzip -dc' 'gzip -c' \
    zst.pgp 'gpg -d | zstd -dc' 'zstd -19 -zc | gpg -e'

For historic reasons filetypes provide limited (case-sensitive) auto-completion capabilities. For example mbox.gz will be found for ? file mbox, provided that corresponding handlers are installed. It will neither find mbox.GZ nor mbox.Gz however, but an explicit ? file mbox.GZ will find and use the handler for gz. [v15 behaviour may differ] The latter mode can only be used for MBOX files.

EML files consist of only one mail message, [v15 behaviour may differ] and can only be opened read-only. When reading MBOX files tolerant POSIX rules are used by default. Invalid message boundaries that can be found quite often in historic MBOX files will be complained about (even more with debug): in this case the method described for mbox-rfc4155 can be used to create a valid MBOX database from the invalid input.

MBOX databases and EML files will always be protected via file-region locks (fcntl(2)) during file operations to protect against concurrent modifications. [Option] An MBOX inbox (MAIL) or “primary system mailbox” will also be protected by so-called dotlock files, the traditional way of mail spool file locking: for any file x a lock file x.lock will be created during the synchronization, in the same directory and with the same user and group identities as the file of interest — as necessary created by an external privileged dotlock helper. dotlock-disable disables dotlock files. Also see “FAQ”: “Howto handle stale dotlock files”.

[Option] If no protocol has been fixated, and name refers to a directory with the subdirectories tmp, new and cur, then it is treated as a folder in “Maildir” format. The maildir format stores each message in its own file, and has been designed so that file locking is not necessary when reading or writing files.

[Option]ally URLs can be used to access network resources, securely via “Encrypted network communication”, if so supported. Network communication socket timeouts are configurable via socket-connect-timeout. All network traffic may be proxied over a SOCKS server via socks-proxy.

[v15-compat]
protocol://[user[:password]@]host[:port][/path]
[no v15-compat] protocol://[user@]host[:port][/path]

[Option]ally supported network protocols are pop3 (POP3) and pop3s (POP3 with TLS encrypted transport), imap and imaps. The [/path] part is valid only for IMAP; there it defaults to INBOX. Network URLs require a special encoding as documented in the section “On URL syntax and credential lookup”.

`folders`

Lists the names of all folders below the given argument or folder 📁 For file-based protocols LISTER will be used for display purposes.

`Followup`, `followup`

(Compose mode)(F, fo) Similar to Reply, and reply, respectively, but save the message in a file named after the local part of the (first) recipient's address, possibly overwriting record, and honouring outfolder. Also see Copy and Save.

`Forward`

(Compose mode) Similar to forward, but saves the message in a file named after the local part of the recipient's address (instead of in record).

`forward`

(Compose mode) Take a message list and the address of a recipient, subject to fullnames, to whom the messages are sent. The text of the original message is included in the new one, enclosed by the values of forward-inject-head and forward-inject-tail. content-description-forwarded-message is inspected. The list of included headers can be filtered with the 'forward' slot of the white- and blacklisting command headerpick. Only the first part of a multipart message is included but for forward-as-attachment.

This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, or was rejected by expandaddr policy, ^ERR-IO if an I/O error occurs, ^ERR-NOTSUP if a necessary character set conversion fails, and ^ERR-INVAL for other errors. It can also fail with errors of “Specifying messages”. Any error stops processing of further messages.

`from` (aka `f`)

Takes a list of message specifications and displays a summary of their message headers, exactly as via headers, making the first message of the result the new “dot” (the last message if showlast is set). An alias of this command is search. Also see “Specifying messages”.

`Fwd`

💀 [Obsolete] Alias for Forward.

`fwd`

💀 [Obsolete] Alias for forward.

`fwdignore`

💀 [Obsolete] Superseded by the multiplexer headerpick.

`fwdretain`

💀 [Obsolete] Superseded by the multiplexer headerpick.

`ghost`, `unghost`

💀 [Obsolete] Replaced by commandalias, uncommandalias.

headerpick, unheaderpick — the multiplexer command for managing your white- and blacklisting of header fields, for a whole bunch of different apps. 💅 [Only new quoting rules] bestie, note that.

No arguments at all? Then it just shows you the set of contexts that actually have settings. Cute, a little overview.

Give it arguments and the first one is the context the command applies to, one of these (case-insensitive):

type — for display purposes (for example type)
save — picks which headers get stored persistently when save, copy, move or even decrypting messages happens. ⚠️ Heads up: MIME related etc. header fields should not be ignored here, otherwise you literally destroy the usability of the message in this case.
forward — for stripping down messages when forwarding a message. Has no effect if forward-as-attachment is set.
top — for defining a user-defined set of fields for the command top.

If the context is the only argument, the current settings of that context get displayed. 🫶

A second argument is the type of restriction you're choosing, and it can be a case-insensitive prefix of retain or ignore, for white- and blacklisting purposes respectively. And listen: establishing a whitelist suppresses inspection of the corresponding blacklist. No cap.

No further argument after that? Then the current settings of the given type get displayed. Otherwise the remaining arguments specify header fields — which [Option]ally may be given as regular expressions — to be added to the given type. The special wildcard field (asterisk, *) establishes a (fast) shorthand setting that covers all fields. ⭐

unheaderpick is the latter one and it always takes three or more arguments, and it's the remover: from the given context, the given type of list, all the given headers will be removed. And the special argument * removes all headers. 🧹

headers (h) — shows the current group of headers. The size of the group depends on the variable screen in interactive mode, and the format can be defined with headline. ✨ If you give it a message-specification, the group of headers containing the first message therein is shown, and the message at the top of the screen becomes the new “dot”. The last message is targeted if showlast is set. 🎯
help (hel) — a synonym for ?. That's it. That's the whole command. 😌
history [Option] — no arguments, or given show, and all history entries are shown (this mode also supports a more verbose output 👀). load will replace the list of entries with the content of history-file, save will dump all entries to said file — replacing former content — and clear will delete all entries. 🗑️

The argument can also be a signed decimal NUMBER, which will select and evaluate the respective history entry, and move it to the top of the history. A negative number is used as an offset to the current command, so that -1 selects the last command, the history top, whereas delete will delete all given entries (:NUMBER:). Also see “On terminal control and line editor”. 🦋

hold (ho, also preserve) — takes a message list and marks each message therein to be saved in the user's system inbox instead of in the “secondary mailbox” MBOX. It does not override the delete command. 💀 And here's the gossip: S-nail deviates from the POSIX standard with this command, because a next command issued after hold will display the following message, not the current one. Periodt.
if (i) — part of the if, elif, else, endif conditional execution construct: if the given condition is true, then the encapsulated block is executed. 🎀 The POSIX standard only supports the (case-insensitive) conditions receive and send — the remaining ones are non-portable extensions. [v15 behaviour may differ] In conjunction with the wysh command prefix(es) “Shell-style argument quoting” and more test operators are available.

if receive
  commands ...
else
  commands ...
endif

Further (case-insensitive) one-argument conditions are terminal — which evaluates to true in interactive terminal sessions (running with standard input or standard output attached to a terminal, and none of the “quickrun” command line options -e, -H and -L have been used) — as well as any boolean value (see “INTERNAL VARIABLES” for textual boolean representations) to mark an enwrapped block as “never execute” or “always execute”. (Remarks: condition syntax errors skip all branches until endif.) 😭

[no v15-compat] and without wysh: it is possible to check “INTERNAL VARIABLES” as well as “ENVIRONMENT” variables for existence, or compare their expansion against a user given value or another variable, by using the $ (“variable next”) conditional trigger character. A variable on the right hand side may be signalled using the same mechanism. Variable names may be enclosed in a pair of matching braces. 🫶 Once this mode has been triggered, several operators are available ([v15-compat] and wysh: they are always available, and there is no trigger — variables will have been expanded by the shell-compatible parser before the if etc. command sees them).

[v15-compat] Two argument conditions. Variables can be tested for existence and expansion: -N tests whether the given variable exists, so that -N editalong evaluates to true when editalong is set, whereas -Z editalong will if it is not. -n "$editalong" will be true if the variable is set and expands to a non-empty string, -z $'\$editalong' only if the expansion is empty, whether the variable exists or not. The remaining conditions take three arguments.

Integer operators treat the arguments on the left and right hand side of the operator as integral numbers and compare them arithmetically. It is an error if any of the operands is not a valid integer — an empty argument (which implies it had been quoted) is treated as if it were 0. Via the question mark ? modifier suffix a saturated operation mode is available, where numbers will linger at the minimum or maximum possible value, instead of overflowing (or trapping). The keyword saturated is optional, so ==?, ==?satu and ==?saturated are therefore identical. Available operators are:

-lt — less than
-le — less than or equal to
-eq — equal
-ne — not equal
-ge — greater than or equal to
-gt — greater than

String and regular expression data operators compare the left and right hand side according to their textual content. Unset variables are treated as the empty string. 🍓 Via the question mark ? modifier suffix a case-insensitive operation mode is available; the keyword case is optional, so ==? and ==?case are identical.

Available string operators are:

< — less than
<= — less than or equal to
== — equal
!= — not equal
>= — greater than or equal to
> — greater than
=% — is substring of
!% — is not substring of

By default these operators work on bytes and (therefore) do not take into account character set specifics. If the case-insensitivity modifier has been used, case is ignored according to the rules of the US-ASCII encoding, i.e., bytes are still compared. ✨

When the [Option]al regular expression support is available, the additional string operators =~ and !~ can be used. They treat the right hand side as an extended regular expression that is matched according to the active locale (see “Character sets”), i.e., character sets should be honoured correctly. 🔥

Conditions can be joined via AND-OR lists (where the AND operator is && and the OR operator is ||), which have equal precedence and will be evaluated with left associativity, thus using the same syntax that is known for the sh(1). It is also possible to form groups of conditions and lists by enclosing them in pairs of brackets [ ... ], which may be interlocked within each other, and also be joined via AND-OR lists. 🌸

The results of individual conditions and entire groups may be modified via unary operators: the unary operator ! will reverse the result.

wysh set v15-compat=yes # with value: automatic "wysh"!
if -N debug;echo *debug* set;else;echo not;endif
if "$ttycharset" == UTF-8 || "$ttycharset" ==?cas UTF8
  echo ttycharset is UTF-8, the former case-sensitive!
endif
set t1=one t2=one
if [ "${t1}" == "${t2}" ]
  echo These two variables are equal
endif
if "$features" =% ,+regex, && "$TERM" =~?case ^xterm.*
  echo ..in an X terminal
endif
if [ [ true ] && [ [ "${debug}" != '' ] || \
    [ "$verbose" != '' ] ] ]
  echo Noisy, noisy
endif
if true && [ -n "$debug" || -n "${verbose}" ]
  echo Left associativity, as is known from the shell
endif

ignore (ig) — identical to discard. Superseded by the multiplexer headerpick. 👋
list — shows the names of all available commands, in command lookup order. [Option] In conjunction with a set variable verbose, additional information will be provided for each command: the argument type will be indicated, the documentation string will be shown, and the set of command flags will show up: 👑
local — yep, this command supports the command modifier local ✨
vput — and this one supports the command modifier vput 💅
*!* — the error number gets tracked in ! (iykyk)
needs-box — whether the command needs an active mailbox, like a folder
ok: — indicators that the command is...
- batch/interactive — usable in interactive or batch mode (-#)
- send-mode — usable in send mode
- subprocess — allowed when running in a subprocess instance, for example from within a macro that's called via on-compose-splice
not ok: — indicators that the command is not...
- compose mode — not available in "Compose mode"
- startup — not available during program startup, like in "Resource files"
gabby — the command produces history-gabby history entries 🗣️

localopts

Okay so this one enforces change localization of the environ (linked) "ENVIRONMENT" and the (global) "INTERNAL VARIABLES" — meaning their state gets reverted back to the former one once the "covered scope" is left 🫶 Just like the command modifier local, which gives block-scope localization for some commands instead, it can only be used inside macro definition blocks introduced by account or define. The covered scope of an account is left once a different account gets activated, and some macros — notably folder-hooks — use their own specific notion of covered scope; here it'll be extended until the folder is left again.

This setting stacks up, bestie: like, if macro1 enables change localization and calls macro2, which explicitly resets localization, then any value changes within macro2 will still be reverted when the scope of macro1 is left. (Caveats tho: if in this example macro2 switches to a different account that sets some variables already covered by localizations, their scope gets extended — and in fact leaving the account will, thus, restore settings in (likely) global scope which actually were defined in a local, macro-private context! 😭)

This command takes one or two arguments. The optional first one specifies an attribute, which may be:

scope — refers to the current scope and is thus the default
call — causes any macro that's being called to be started with localization enabled by default
call-fixate — (if enabled) disallows any called macro from turning off localization: like this it can be ensured that once the current scope regains control, any changes made in deeper levels have been reverted

The latter two are mutually exclusive, and neither affects xcall. The (second) argument is interpreted as a boolean (string, see "INTERNAL VARIABLES") and states whether the given attribute shall be turned on or off 👑

define temporary_settings {
  set possibly_global_option1
  localopts on
  set localized_option1
  set localized_option2
  localopts scope off
  set possibly_global_option2
}

Lfollowup, Lreply

(Compose mode) Reply to messages that come in via known (mlist) or subscribed (mlsubscribe) mailing lists, or pretend to do so (see "Mailing lists") 💌 On top of the usual followup and reply, respectively, functionality, this will actively resort and even remove message recipients in order to generate a message that's supposed to be sent to a mailing list. For example it'll also implicitly generate a Mail-Followup-To: header if that seems useful, regardless of the setting of the variable followup-to. For more documentation please refer to "On sending mail, and non-interactive mode".

This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, ^ERR-PERM if some addressees were rejected by expandaddr, ^ERR-IO if an I/O error occurs, ^ERR-NOTSUP if a necessary character set conversion fails, and ^ERR-INVAL for other errors. It can also fail with errors of "Specifying messages". Occurrence of some of the errors depends on the value of expandaddr. Any error stops processing of further messages 🛑

Mail

(Compose mode) Similar to mail, but saves the message in a file named after the local part of the first recipient's address (instead of in record) 📥

mail

(Compose mode)(m) Takes a (list of) recipient address(es) as (an) argument(s), or asks on standard input if none were given; then collects the remaining mail content and sends it out. Unless the internal variable fullnames is set, recipient addresses will be stripped from comments, names etc. For more documentation please refer to "On sending mail, and non-interactive mode".

This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, ^ERR-PERM if some addressees were rejected by expandaddr, ^ERR-NOTSUP if multiple messages have been specified, ^ERR-IO if an I/O error occurs, ^ERR-NOTSUP if a necessary character set conversion fails, and ^ERR-INVAL for other errors. It can also fail with errors of "Specifying messages". Occurrence of some of the errors depends on the value of expandaddr ✨

mailcap

[Option] When used without arguments, or if show has been given, the content of "The Mailcap files" cache is shown, (re-)initializing it first as necessary. If the argument is load then the cache will only be (re-)initialized, and clear will remove its contents. Note that S-nail will try to load the files only once — use mailcap clear to unlock further attempts. Loading and parsing can be made more verbose 🔍

mbox

(mb) The given message list is to be sent to the "secondary mailbox" MBOX when S-nail is quit; this is the default action unless the variable hold is set. [v15 behaviour may differ] This command can only be used in a "primary system mailbox" 📦

mimetype, unmimetype

[Only new quoting rules] Without arguments, the content of the MIME type cache will be displayed; a more verbose listing will be produced if either of debug or verbose are set. When given arguments, they'll be joined, interpreted as shown in "The mime.types files" (also see "HTML mail and MIME attachments"), and the resulting entry will be added (prepended) to the cache. In any event MIME type sources are loaded first as necessary — mimetypes-load-control can be used to fine-tune which sources are actually loaded 🎀

The latter command deletes all specifications of the given MIME type, thus ? unmimetype text/plain will remove all registered specifications for the MIME type text/plain. The special name * will discard all existing MIME types, just as will reset — but reset also reenables cache initialization via mimetypes-load-control 🦋

mimeview

[v15 behaviour may differ] Only available in interactive mode, this command allows execution of external MIME type handlers which don't integrate into the normal type output (see "HTML mail and MIME attachments"). ([v15 behaviour may differ] No syntax to directly address parts, this restriction may vanish.) The user will be asked, for each non-text part of the given message in turn, whether the registered handler shall be used to display the part 👀

mlist, unmlist

[Only new quoting rules] Manage the list of known "Mailing lists"; subscriptions are controlled via mlsubscribe. The latter command deletes all given arguments, or all at once when given the asterisk *. The former shows the list of all currently known lists if used without arguments; otherwise the given arguments will become known. [Option] In the latter case, arguments which contain any of the "magic regular expression characters" will be interpreted as one, possibly matching many addresses — these will be sequentially matched via linked lists instead of being looked up in a dictionary 🧚

mlsubscribe, unmlsubscribe

Building upon the command pair mlist, unmlist, but only managing the subscription attribute of mailing lists. (The former will also create not-yet-existing mailing lists.) 💜

Move

Similar to move, but move the messages to a file named after the local part of the sender of the first message instead of taking a filename argument; outfolder is inspected to decide on the actual storage location 📁

move

Acts like copy but marks the messages for deletion if they were transferred successfully ✂️

Like more, but also displays header fields which would not pass the headerpick selection, and all MIME parts. Identical to Page 🌸

Invokes the PAGER on the given messages, even in non-interactive mode and as long as the standard output is a terminal. Identical to page 📄

mtaaliases

[Option] When used without arguments, or if show has been given, the content of the mta-aliases cache is shown, (re-)initializing it first as necessary. If the argument is load then the cache will only be (re-)initialized, and clear will remove its contents 🍓

netrc [Option] — run it with no argument (or with the argument show) and it shows you the content of the ~/.netrc cache, initializing it as necessary. Argument load means the cache gets (re)loaded, and clear removes it. Loading and parsing can both be made more verbose. lookup queries the cache for the URL you pass as the second argument ([USER@]HOST). Go peep netrc-lookup, netrc-pipe and the section “On URL syntax and credential lookup” — and the section “The .netrc file” documents the file format in full detail. 💅
newmail — checks for new mail in the current folder without committing any changes first. If new mail is present, a message is shown. If the header variable is set, the headers of each new message are shown too. Ngl this command is not available for all mailbox types. 🫶
next (n) — (like + or “ENTER”) goes to the next message in sequence and types it. With an argument list, it types the next matching message. ✨
New — same as Unread. (Yes bestie, the capitalisation is the whole personality here 👑)
new — same as unread. (lowercase icon behaviour 💀)
noop — if the current folder is accessed via a network connection, a “NOOP” command is sent; otherwise no operation is performed. Literally does nothing, and it slays at it. 🌸
Page — like page, but it also displays header fields which would not pass the headerpick selection, and all MIME parts. Identical to More.
page — invokes the PAGER on the given messages, even in non-interactive mode, and as long as the standard output is a terminal. Identical to more.
Pipe — like pipe but also pipes header fields which would not pass the headerpick selection, and all parts of MIME multipart/alternative messages. 🦋
pipe (pi) — takes an optional message list and shell command (that defaults to cmd), and pipes the messages through the command. If the page variable is set, every message is followed by a formfeed character.
preserve (pre) — a synonym for hold.
Print (P) — alias for Type.
print (p) — Research Unix equivalent of type.
quit (q) — terminates the session, saving all undeleted, unsaved messages in the current “secondary mailbox” MBOX, preserving all messages marked with hold or preserve or never referenced in the system inbox, and removing all other messages from the “primary system mailbox”. If new mail arrived during the session, the message “You have new mail” will be shown. If given while editing a mailbox file with the command line option -f, then the edit file is rewritten. A return to the shell is effected, unless the rewrite of edit file fails, in which case the user can escape with the exit command. The optional status number argument will be passed through to exit(3). [v15 behaviour may differ] For now it can happen that the given status will be overwritten; later this will only occur if a later error needs to be reported onto an otherwise success indicating status. 😭
read [Only new quoting rules] — reads a line from standard input, or from the channel set active via readctl, and assigns the data — which will be split as indicated by ifs — to the given variables. The variable names are checked by the same rules as documented for vput, and the same error codes will be seen in !; the exit status ? indicates the number of bytes read, it will be -1 with the error number ! set to ^ERR-BADF in case of I/O errors, or ^ERR-NONE upon End-Of-File. If there are more fields than variables, it assigns successive fields to the last given variable. If there are less fields than variables, it assigns the empty string to the remains. 💖

? read a b c
   H  e  l  l  o
? echo "<$a> <$b> <$c>"
<H> <e> <l  l  o>
? wysh set ifs=:; read a b c;unset ifs
hey2.0,:"'you    ",:world!:mars.:
? echo $?/$^ERRNAME / <$a><$b><$c>
0/NONE / <hey2.0,><"'you    ",><world!:mars.:><><>

readsh [Only new quoting rules] — like read, but it splits on shell token boundaries (see “Shell-style argument quoting”) rather than at ifs. [v15 behaviour may differ] Could become a commandalias, maybe read --tokenize --. 🐚
readall [Only new quoting rules] — reads anything from standard input, or from the channel set active via readctl, and assigns the data to the given variable. The variable name is checked by the same rules as documented for vput, and the same error codes will be seen in !; the exit status ? indicates the number of bytes read, it will be -1 with the error number ! set to ^ERR-BADF in case of I/O errors, or ^ERR-NONE upon End-Of-File. [v15 behaviour may differ] The input data length is restricted to 31-bits. ⭐
readctl [Only new quoting rules] — manages input channels for read, readsh and readall, to be used to avoid complicated or impracticable code, like calling read from within a macro in non-interactive mode. Without arguments, or when the first argument is show, a listing of all known channels is printed. Channels can otherwise be created, and existing channels can be set active and removed by giving the string used for creation. 🎀

The channel name is expected to be a file descriptor number, or, if parsing the numeric fails, an input file name that undergoes “Filename transformations”. For example (this example requires a modern shell):

$ printf 'echon "hey, "\nread a\nyou\necho $a' |\
  s-nail -R#
hey, you
$ LC_ALL=C printf 'echon "hey, "\nread a\necho $a' |\
  LC_ALL=C 6<<< 'you' s-nail -R#X'readctl create 6'
hey, you

remove [Only new quoting rules] — removes the named files or directories. If a name refers to a mailbox, say a Maildir mailbox, then a mailbox type specific removal will be performed, deleting the complete mailbox. In interactive mode the user is asked for confirmation. 💀 (no undo, bestie, so maybe read that twice)
rename [Only new quoting rules] — takes the name of an existing folder and the name for the new folder, and renames the first to the second one. “Filename transformations” including shell pathname wildcard pattern expansions (glob(7)) are performed on both arguments. Both folders must be of the same type. 🔥
Reply, Respond — (Compose mode)(R) identical to reply except that it replies to only the sender of each message of the given list, by using the first message as the template to quote, for the ‘Subject:’ etc.; setting flipr will exchange this command with reply. 🫶
reply, respond — (Compose mode)(r) take a message (list) and group-respond (to each in turn) by addressing the sender and all recipients, subject to fullnames and alternates processing. followup-to, followup-to-honour, reply-to-honour as well as recipients-in-cc influence response behaviour. quote as well as quote-as-attachment configure whether the responded-to message shall be quoted etc., and content-description-quote-attachment may be used. Setting flipr will exchange this command with Reply. The command Lreply offers special support for replying to mailing lists. For more documentation please refer to “On sending mail, and non-interactive mode”. ✨

Resend — like resend, but does not add any header lines. Fa la pena saying: this is not a way to hide the sender's identity, it's just useful for sending a message again to the same recipients. 🙈
resend — takes a list of messages and a name, and sends each message to the given addressee, which is subject to fullnames. ‘Resent-From:’ and related header fields are prepended to the new copy of the message. Saving in record is only performed if record-resent is set. [v15 behaviour may differ] (Compose mode) is not entered, the only supported hooks are on-resend-enter and on-resend-cleanup. 💌

retain (ret) — superseded by the multiplexer headerpick. 👋 (rip bozo, respectfully)
return — only available inside of a defined macro or an account, this command returns control of execution to the outer scope. The two optional parameters are positive decimal numbers and default to 0: the first specifies the 32-bit return value (stored in ? [v15 behaviour may differ] and later extended to 64-bit), the second the 32-bit error number (stored in !). As documented for ? a non-0 exit status may cause the program to exit. 🌀
Save (S) — similar to save, but saves the messages in a file named after the local part of the sender of the first message instead of taking a filename argument; outfolder is inspected to decide on the actual storage location. 🌈

🌸 save

Okay bestie, save (aka s) takes a message list plus a filename and appends each message in turn to the end of that file 💖. “Filename transformations” get applied — including shell pathname wildcard pattern expansions (glob(7)) — on the filename ✨. If you don't hand it a filename, it uses the “secondary mailbox” MBOX. The filename, in quotes, followed by the generated character count, gets echoed on the user's terminal 🎀.

If you're editing a “primary system mailbox”, the messages get marked for deletion 👀. And if you want to filter the saved header fields down to just the subset you actually want, use the ‘save’ slot of the white- and blacklisting command headerpick. Also see Copy 🫶.

💅 savediscard

[Obsolete] Superseded by the multiplexer headerpick. That's it, that's the whole vibe 💀.

💅 saveignore

[Obsolete] Superseded by the multiplexer headerpick. Same energy, iconic and retired ✨.

💅 saveretain

[Obsolete] Superseded by the multiplexer headerpick. No cap, it's just living in the past now 🎀.

🔍 search

Takes a message specification (list) and displays a header summary of all the matching messages, as via headers 👑. This command is literally an alias of from. Also see “Specifying messages” 💖.

👀 seen

Takes a message list and marks all of them as having been read. The way that's so satisfying, ngl 🌸.

🎀 set, unset

set is also se, and unset is [Only new quoting rules] uns ✨.

The latter command (unset) will delete all given global variables — or only block-scope local ones if the local command modifier has been used 💅.

The former (set), when used without arguments, will show all currently known variables, being more verbose if either debug or verbose is set 👑.

Remarks: this list mode will not automatically link-in (known) “ENVIRONMENT” variables. That only happens for explicit addressing — examples are varshow, using a variable in an if condition or a string passed to echo, explicit setting, as well as some program-internal use cases (look-ups) 🫶.

Otherwise, the given variables (and arguments) are set or adjusted 🎀. Arguments are of the form ‘name=value’ (no space before or after ‘=’), or plain ‘name’ if there is no value, i.e., a boolean variable. If a name begins with ‘no’, as in ‘set nosave’, the effect is the same as invoking the unset command with the remaining part of the variable (‘unset save’) 💖.

[v15 behaviour may differ] In conjunction with the wysh (or local) command prefix(es), “Shell-style argument quoting” can be used to quote arguments as necessary. [v15 behaviour may differ] Otherwise quotation marks may be placed around any part of the assignment statement to quote blanks or tabs ✨.

When operating in global scope, any ‘name’ that is known to map to an environment variable will automatically cause updates in the program environment — unsetting a variable in the environment requires corresponding system support — so use the command environ for further environmental control 🌈.

If the command modifier local has been used to enforce local scoping, then the given user variables will be garbage collected when the local scope is left; for “INTERNAL VARIABLES”, however, local behaves the same as if localopts would have been set (temporarily), which means that changes are inherited by deeper scopes 👀. Also see varshow and the sections “INTERNAL VARIABLES” and “ENVIRONMENT” 💜.

? wysh set indentprefix=' -> '
? wysh set atab=$'' aspace=' ' zero=0

🐚 shcodec

Apply shell quoting rules to the given raw-data arguments 🎀. Supports vput (see “Command modifiers”). The first argument specifies the operation: [+]e[ncode] or d[ecode] cause shell quoting to be applied to the remains of the line, and expanded away thereof, respectively ✨.

If the former is prefixed with a plus-sign, the quoted result will not be roundtrip enabled, and thus can be decoded only in the very same environment that was used to perform the encode; also see mle-quote-rndtrip 👑.

If the coding operation fails, the error number ! is set to ^ERR-CANCELED, and the unmodified input is used as the result; the error number may change again due to output or result storage errors 💀.

🦋 shell

[Only new quoting rules] — aka sh — invokes an interactive version of the shell, and returns its exit status 💅. Periodt.

🎀 shortcut, unshortcut

[Only new quoting rules] Manage the file- or pathname shortcuts as documented for folder 🌸.

The latter command (unshortcut) deletes all shortcuts given as arguments, or all at once when given the asterisk ‘*’ ✨.

The former (shortcut) shows the list of all currently defined shortcuts if used without arguments, or the target of the given one with a single argument 👑. Otherwise arguments are treated as pairs of shortcuts and their desired expansion, creating new or updating already existing ones 💖.

🧚 shift

[Only new quoting rules] Shift the positional parameter stack (starting at 1) by the given number (which must be a positive decimal), or 1 if no argument has been given 🎀.

It's an error if the value exceeds the number of positional parameters. If the given number is 0, no action is performed — successfully 😌✨.

The stack as such can be managed via vpospar 🫶. Note this command will fail in account and hook macros unless the positional parameter stack has been explicitly created in the current context via vpospar 👀.

🍓 show

Like type, but performs neither MIME decoding nor decryption, so that the raw message text is shown 💀. Raw and unfiltered, main character energy.

📏 size

(si) Shows the size in characters of each message of the given message list 🌸.

😴 sleep

[Only new quoting rules] Sleep for the specified number of seconds (and optionally milliseconds), by default interruptible 💤.

If a third argument is given, the sleep will be uninterruptible; otherwise the error number ! will be set to ^ERR-INTR if the sleep has been interrupted 👀.

The command will fail and the error number will be ^ERR-OVERFLOW if the given duration(s) overflow the time datatype, and ^ERR-INVAL if the given durations are no valid integers 💅.

🔥 sort, unsort

The latter command (unsort) disables sorted or threaded mode, returns to normal message order and, if the header variable is set, displays a header summary 🌈.

The former (sort) shows the current sorting criterion when used without an argument, but creates a sorted representation of the current folder otherwise, and changes the next command and the addressing modes such that they refer to messages in the sorted order ✨. Message numbers are the same as in regular mode. If the header variable is set, a header summary in the new order is also displayed 👑.

Automatic folder sorting can be enabled by setting the autosort variable, as in ‘set autosort=thread’ 💖.

Possible sorting criterions are:

date — Sort the messages by their ‘Date:’ field, that is by the time they were sent 🎀.
from — Sort messages by the value of their ‘From:’ field, that is by the address of the sender. If the showname variable is set, the sender's real name (if any) is used 🌸.
size — Sort the messages by their size 📏.
spam — [Option] Sort the message by their spam score, as has been classified by spamrate 💀.
status — Sort the messages by their message status 👀.
subject — Sort the messages by their subject ✨.
thread — Create a threaded display 🧵.
to — Sort messages by the value of their ‘To:’ field, that is by the address of the recipient. If the showname variable is set, the recipient's real name (if any) is used 💜.

🌟 source

[Only new quoting rules] — aka so — the source command reads commands from the given file 📖. “Filename transformations” will be applied ✨.

If the given expanded argument ends with a vertical bar ‘|’, then the argument will instead be interpreted as a shell command and S-nail will read the output generated by it 🫶.

Dependent on the settings of posix and errexit, and also dependent on whether the command modifier ignerr had been used, encountering errors will stop sourcing of the given input 👀.

[v15 behaviour may differ] Note that source cannot be used from within macros that execute as folder-hooks or accounts, i.e., it can only be called from macros that were called 💅.

🌈 source_if

[Only new quoting rules] The difference to source (beside not supporting pipe syntax aka shell command input) is that this command will not generate an error nor warn if the given file argument cannot be opened successfully 😌✨. Gentle, forgiving, unbothered.

💀 spamclear

[Option] Takes a list of messages and clears their ‘is-spam’ flag 🧹.

🙈 spamforget

[Option] Takes a list of messages and causes the spam-interface to forget it has ever used them to train its Bayesian filter 🧠✨.

Unless otherwise noted, the ‘is-spam’ flag of the message is inspected to chose whether a message shall be forgotten to be “ham” or “spam” 👀.

🍖 spamham

[Option] Takes a list of messages and informs the Bayesian filter of the spam-interface that they are “ham” 🥓. This also clears the ‘is-spam’ flag of the messages in question 💖.

⭐ spamrate

[Option] Takes a list of messages and rates them using the configured spam-interface, without modifying the messages, but setting their ‘is-spam’ flag as appropriate 📊. Because the spam rating headers are lost, the rate will be forgotten once the mailbox is left 💀.

Refer to the manual section “Handling spam” for the complete picture of spam handling in S-nail 👑.

🎀 spamset

[Option] Takes a list of messages and sets their ‘is-spam’ flag 🚩. Iconic.

`spamspam`

[Option] Takes a list of messages and tells the Bayesian filter of the spam-interface that they are “spam”. It also sets the ‘is-spam’ flag on those messages, so like… yeah, they're marked 💀

`thread`

[Obsolete] Same thing as ‘sort thread’ (consider using a ‘commandalias’ if you need it, bestie).

`tls`

[Only new quoting rules] This is the TLS information-and-management command multiplexer — it's here to help with “Encrypted network communication”, and honestly it's mostly only available if the term ‘,+sockets,’ is included in features ✨. Commands support vput if they say so (peep “Command modifiers”). When errors happen the result shown is always the empty string, and you can spot errors via the error number !. For example, string length overflows get caught and ! gets set to ^ERR-OVERFLOW. The TLS configuration is honoured — especially tls-verify. 👑

? vput tls result fingerprint pop3s://ex.am.ple
? echo $?/$!/$^ERRNAME: $result

certchain — Shows the complete verified peer certificate chain. It also includes informational fields when you're in conjunction with verbose.
certificate — Shows only the peer certificate, with no signers at all. Includes informational fields in conjunction with verbose.
fingerprint — Shows the tls-fingerprint-digested fingerprint of the certificate of the given HOST (‘server:port’, where the port defaults to the HTTPS port, 443). tls-fingerprint is actively ignored for the runtime of this command.

`Top`

Like top, but it always uses the headerpick ‘type’ slot for white- and blacklisting header fields. Consistent queen behavior 💅

`top`

(to) Takes a message list and types out the first toplines lines of each message on the user's terminal. Unless a special selection has been established for the ‘top’ slot of the headerpick command, the only header fields displayed are ‘From:’, ‘To:’, ‘Cc:’, and ‘Subject:’. Top will always use the ‘type’ headerpick selection instead. You can apply compression to what's displayed by setting topsqueeze. Messages get decrypted and converted to the terminal character set if necessary 🫶

`touch`

(tou) Takes a message list and marks the messages for saving in the “secondary mailbox” MBOX. Heads up: S-nail deviates from the POSIX standard with this command — a following next command will display the following message instead of the current one. Not me being different, it's just how it is 🙈

`Type`

(T) Like type, but it also displays header fields which would not pass the headerpick selection, plus all visualizable parts of MIME ‘multipart/alternative’ messages. Iconic, honestly.

`type`

(t) Takes a message list and types out each message on the user's terminal. The display of message headers is selectable via headerpick. For MIME multipart messages: all parts with a content type of ‘text’, all parts which have a registered MIME type handler (see “HTML mail and MIME attachments”) that produces plain text output, and all ‘message’ parts are shown — everything else is hidden except for its headers. Messages are decrypted and converted to the terminal character set if necessary. And if you've got parts that just won't display as plain text, the mimeview command can display them for you 🌸

`unaccount`

See account.

`unalias`

(una) See alias.

`unanswered`

See answered.

`unbind`

See bind.

`uncollapse`

See collapse.

`uncolour`

See colour.

`undefine`

See define.

`undelete`

See delete.

`undraft`

See draft.

`unflag`

See flag.

`unfwdignore`

[Obsolete] Superseded by the multiplexer headerpick.

`unfwdretain`

[Obsolete] Superseded by the multiplexer headerpick.

`unignore`

Superseded by the multiplexer headerpick.

`unmimetype`

See mimetype.

`unmlist`

See mlist.

`unmlsubscribe`

See mlsubscribe.

`Unread`

Same as unread.

`unread`

Takes a message list and marks each message as not having been read. Rewind the vibe check ⏪

`unretain`

Superseded by the multiplexer headerpick.

`unsaveignore`

[Obsolete] Superseded by the multiplexer headerpick.

`unsaveretain`

[Obsolete] Superseded by the multiplexer headerpick.

`unset`

[Only new quoting rules] (uns) See set.

`unshortcut`

See shortcut.

`unsort`

See short.

`unthread`

[Obsolete] Same as unsort.

`urlcodec`

Performs URL percent codec operations on the raw-data argument, according to RFC 3986 ✨. The first argument specifies the operation: e[ncode] or d[ecode] perform plain URL percent en- and decoding, respectively. p[ath]enc[ode] and p[ath]dec[ode] perform a slightly modified operation which should be better for pathnames: it does not allow a tilde ‘~’, and will neither accept hyphen-minus ‘-’ nor dot '' as an initial character. The remains of the line form the URL data which is to be converted. This is a character set agnostic operation, so it may absolutely decode bytes which are invalid in the current ttycharset — no cap 🧚

It supports vput (see “Command modifiers”), and it manages the error number !. If the coding operation fails, the error number ! is set to ^ERR-CANCELED, and the unmodified input is used as the result; the error number may change again due to output or result storage errors. [v15 behaviour may differ] This command does not know about URLs beside what is documented. (vexpr offers a makeprint subcommand, shall the URL be displayed.)

`varshow`

[Only new quoting rules] This command produces the same output as the listing mode of set, including verboseity adjustments, but only for the given variables. Just the ones you asked for, bestie 💖

`verify`

[Option] Takes a message list and verifies each message. If a message is not a S/MIME signed message, verification will fail for it. The verification process checks if the message was signed using a valid certificate, if the message sender's email address matches one of those contained within the certificate, and if the message content has been altered. Detective mode activated 🔍

`version`

Shows the version and features of S-nail, optionally in a more verbose form which also includes the build and running system environment. This command supports vput (see “Command modifiers”).

`vexpr`

[Only new quoting rules] A multiplexer command which offers signed 64-bit numeric calculations, as well as other, mostly string-based operations. C-style byte string operations are available via csop. The first argument defines the number, type, and meaning of the remaining arguments. An empty number argument is treated as 0. It supports vput (see “Command modifiers”). The result shown in case of errors is ‘-1’ for usage errors and numeric operations, and the empty string otherwise; “soft” errors, like when a search operation failed, will also set the ! error number to ^ERR-NODATA. Except when otherwise noted, numeric arguments are parsed as signed 64-bit numbers, and errors will be reported in the error number ! as the numeric error ^ERR-RANGE. 🌈

Numeric operations work on one or two signed 64-bit integers. Numbers prefixed with ‘0x’ or ‘0X’ are interpreted as hexadecimal (base 16) numbers, whereas ‘0’ indicates octal (base 8), and ‘0b’ as well as ‘0B’ denote binary (base 2) numbers. You can use any base in between 2 and 36, inclusive, with the ‘BASE#number’ notation, where the base is given as an unsigned decimal number — so ‘16#AFFE’ is a different way of specifying a hexadecimal number. Unsigned interpretation of a number can be enforced by prefixing an ‘u’ (case-insensitively), as in ‘u-110’; this is not necessary for power-of-two bases (2, 4, 8, 16 and 32), which will be interpreted as unsigned by default, but it still makes a difference regarding overflow detection and overflow constant. You can also enforce signed interpretation by (instead) prefixing an ‘s’ (case-insensitively). The number sign notation uses a permissive parse mode and as such supports complicated conditions out of the box:

? wysh set ifs=:;read i;unset ifs;echo $i;vexpr pb 2 10#$i
   -009
<   -009>
0b1001

One integer is expected by assignment (equals sign ‘=’), which does nothing but parse the argument — thus detecting validity and possible overflow conditions — unary not (tilde ‘~’), which creates the bitwise complement, and unary plus and minus. Two integers are used by addition (plus sign ‘+’), subtraction (hyphen-minus ‘-’), multiplication (asterisk ‘*’), division (solidus ‘/’) and modulo (percent sign ‘%’), as well as for the bitwise operators logical or (vertical bar ‘|’, to be quoted), bitwise and (ampersand ‘&’, to be quoted), bitwise xor (circumflex ‘^’), the bitwise signed left- and right shifts (‘<<’, ‘>>’), as well as for the unsigned right shift ‘>>>’. 🎀

Another numeric operation is pbase, which takes a number base in between 2 and 36, inclusive, and will act on the second number given just the same as what equals sign ‘=’ does — but the number result will be formatted in the base given, as a signed 64-bit number unless unsigned interpretation of the input number had been forced (with an u prefix). Ate, no crumbs 💅

okay so numeric operations have a whole extra mode and it's called saturated, and you turn it on with the question mark ? modifier suffix. The keyword saturated is optional — so +?, +?satu, and +?saturated are literally identical, no cap. 💅

In saturated mode, overflow errors and division and modulo by zero are no longer reported via the exit status — instead the result just lingers 😭 at the minimum or maximum possible value instead of overflowing (or trapping). Which is honestly a vibe. This is true also for the argument parse step. For the bitwise shifts, the saturated maximum is 63. And any caught overflow will be reported via the error number ! as ^ERR-OVERFLOW. 🫶

? vput vexpr res -? +1 -9223372036854775808
? echo $?/$!/$^ERRNAME:$res
0/75/OVERFLOW:-9223372036854775808

heads up bestie — character set agnostic string functions have no notion of locale settings and character sets. Like, none. Zero. 🙈

date-utc — outputs the current date and time in UTC (Coordinated Universal Time), with the values named such that vput vexpr x date-utc; eval wysh set $x creates accessible variables ✨
date-stamp-utc — outputs a RFC 3339 internet date/time format of UTC 🕰️
epoch — the seconds and nanoseconds since the Unix epoch (1970-01-01T00:00:00), named epoch_sec and epoch_nsec such that vput vexpr x epoch; eval wysh set $x creates accessible variables ⏳
file-expand — performs the usual “Filename transformations” on its argument 🗂️
file-stat, file-lstat — perform the usual “Filename transformations” on the argument, then call stat(2) and lstat(2) respectively, and output values such that vput vexpr x file-stat FILE; eval wysh set $x creates accessible variables. The variable st_type uses a solidus / to denote directories, commercial at @ for links, number sign # for block devices, percent sign % for character devices, vertical bar | for FIFOs, equal sign = for sockets, and the period . for the rest 🦋
random — generates a random string of the given length, or of PATH_MAX bytes (a constant from /usr/include) if the value 0 is given; the random string will be base64url encoded according to RFC 4648, and thus be usable as a (portable) filename 🎲

String operations work — sufficient support provided — according to the active user's locale encoding and character set (see “Character sets”). Where the question mark ? modifier suffix is supported, there's a case-insensitive operation mode available; the keyword case is optional, so regex? and regex?case are therefore identical. icon behaviour tbh 👑

makeprint — (one-way) converts the argument to something safely printable on the terminal 🖨️
regex — [Option] a string operation that will try to match the first argument with the regular expression given as the second argument. The ? modifier suffix is supported. If the optional third argument has been given then, instead of showing the match offset, a replacement operation is performed: the third argument is treated as if specified within dollar-single-quote (see “Shell-style argument quoting”), and any occurrence of a positional parameter — for example 0, 1 etc. — is replaced with the according match group of the regular expression 🔍

? vput vexpr res regex bananarama \
    (.*)NanA(.*) '\${1}au\$2'
? echo $?/$!/$^ERRNAME:$res:
1/61/NODATA::
? vput vexpr res regex?case bananarama \
    (.*)NanA(.*) '\${1}uauf\$2'
? echo $?/$!/$^ERRNAME:$res:
0/0/NONE:bauauframa:

vpospar — [Only new quoting rules] manages the positional parameter stack (see 1, #, *, @ as well as shift). If the first argument is clear, then the positional parameter stack of the current context — or the global one, if there is none — is cleared. If it's set, then the remaining arguments will be used to (re)create the stack; if the parameter stack size limit gets excessed, an ^ERR-OVERFLOW error will occur 😤

If the first argument is quote, a round-trip capable representation of the stack contents is created, with each quoted parameter separated from each other with the first character of ifs, and followed by the first character of if-ws if that is not empty and not identical to the first. If that results in no separation at all, a space character is used. This mode supports vput (see “Command modifiers”). I.e. the subcommands set and quote can be used (in conjunction with eval) to (re)create an argument stack from and to a single variable losslessly ✨

? vpospar set hey, "'you    ", world!
? echo $#: <${1}><${2}><${3}>
? vput vpospar x quote
? vpospar clear
? echo $#: <${1}><${2}><${3}>
? eval vpospar set ${x}
? echo $#: <${1}><${2}><${3}>

visual — (v) takes a message list and invokes the VISUAL display editor on each message. Modified contents are discarded unless the writebackedited variable is set, and are not used unless the mailbox can be written to and the editor returns a successful exit status. edit can be used instead for a less display oriented editor 🎨

write — (w) for conventional messages, the body without all headers is written. The original message is never marked for deletion in the originating mail folder. The output is decrypted and converted to its native format as necessary. If the output file exists, the text is appended. If a message is in MIME multipart format, its first part is written to the specified file as for conventional messages; handling of the remains depends on the execution mode. No special handling of compressed files is performed 💾

In interactive mode the user is consecutively asked for the filenames of the processed parts. For convenience, saving of each part may be skipped by giving an empty value — the same result as writing it to /dev/null. Shell piping the part content by specifying a leading vertical bar | character for the filename is supported. Other user input undergoes the usual “Filename transformations”, including shell pathname wildcard pattern expansions (glob(7)) and shell variable expansion for the message as such, not the individual parts, and contents of the destination file are overwritten if the file previously existed. Character set conversion to ttycharset is performed when saving text data 🫶

[v15 behaviour may differ] In non-interactive mode any part which does not specify a filename is ignored, and suspicious parts of filenames of the remaining parts are URL percent encoded (as via urlcodec) to prevent injection of malicious character sequences, resulting in a filename that will be written into the current directory. Existing files will not be overwritten — instead the part number or a dot are appended after a number sign # to the name until file creation succeeds (or fails due to other reasons). 😭

xcall — [Only new quoting rules] the sole difference to call is that the new macro is executed in place of the current one, which will not regain control: all resources of the current macro will be released first. This implies that any setting covered by localopts will be forgotten and covered variables will become cleaned up. If this command is not used from within a called macro, it will silently be (a more expensive variant of) call 💫

xit — (x) a synonym for exit. That's it. That's the whole thing 👋

z — [Only new quoting rules] S-nail presents message headers in screenfuls as described under the headers command. Without arguments, this command scrolls to the next window of messages — likewise if the argument is +. An argument of - scrolls to the last, ^ scrolls to the first, and $ to the last screen of messages. A number argument prefixed by + or - indicates that the window is calculated in relation to the current position, and a number without a prefix specifies an absolute position 📜

Z — [Only new quoting rules] similar to z, but scrolls to the next or previous window that contains at least one new or flagged message. The main-character version of z, honestly 👑

✨ COMMAND ESCAPES ✨

Command escapes are available in “Compose mode” during interactive usage, when explicitly requested via -~, and in batch mode (-#). They perform special functions — like editing headers of the message being composed, calling normal “COMMANDS”, yielding a shell, etc. 🐚 Command escapes are only recognized at the beginning of lines, and consist of an escape followed by a command character. The default escape character is the tilde ~ 🎀

Unless otherwise documented, command escapes ensure proper updates of the error number ! and the exit status ?. The variable errexit controls whether a failed operation errors out message compose mode and causes program exit. Escapes may be prefixed by none to multiple single character command modifiers, and interspersed whitespace is ignored:

An effect equivalent to the command modifier ignerr can be achieved with hyphen-minus -, overriding errexit 🙈
The modifier dollar $ evaluates the remains of the line; also see “Shell-style argument quoting”. [v15 behaviour may differ] For now the entire input line is evaluated as a whole, so to avoid control operators like semicolon ; getting interpreted when you so did not mean it, they must be quoted. 💅

You can stop a command line from being added to the [Option]al history by dropping a whitespace directly after the escape. The [Option]al key bindings support a compose mode specific context. Okay so here's the lineup — the following command escapes are supported, bestie: ✨

~~ string — Insert the string of text into the message, prefaced by a single ~. (If the escape character itself has been changed, then that character must be doubled instead. iykyk 🫶)
~! command — Execute the shell command that follows, replacing unescaped exclamation marks with the previously executed command if the internal variable bang is set, then bounce right back to the message. 🔥
~. — End compose mode and send the message. The hooks on-compose-splice-shell and on-compose-splice, in order, will be called when set, after which, in interactive mode, askatend (leading to askcc, askbcc) and askattach will be checked as well as asksend, after which a set on-compose-leave hook will be called, autocc and autobcc will be joined in if set, and finally a given message-inject-tail will be incorporated — after which the compose mode is left. She's a whole production, no cap. 🎬
~: S-nail-command or ~_ S-nail-command — Lets you execute the “COMMANDS” (the ones that are allowed in compose mode, anyway).
~< filename — Identical to ~r. same energy, different key. 💫
~<! command — command is executed using the shell, and its standard output gets inserted into the message.
~? — [Option] Write a summary of command escapes. the cheat sheet moment. 📋
~@ [filename...] — Append to or edit the list of attachments. Lowkey important: this does not manage the error number ! and the exit status ? (please use ~^ if error handling is necessary, babe). The append mode expects a list of filename arguments as shell tokens (see “Shell-style argument quoting”; token-separating commas are ignored, too), to be interpreted as documented for the command line option -a, with the message number exception as described below. 🌸

Without filename arguments the attachment list is edited, entry by entry; if a filename is left empty, that attachment is deleted from the list; once the end of the list is reached, either new attachments may be entered or the session can be quit by committing an empty “new” attachment. In non-interactive mode or in batch mode (-#) the list of attachments is effectively not edited but instead recreated; again, an empty input ends list creation. 🦋

For all modes, if a given filename solely consists of the number sign # followed by either a valid message number of the currently active mailbox, or by a period ., referring to the current message of the active mailbox — the so-called “dot” — then the given message is attached as a message/rfc822 MIME message part. The number sign must be quoted to avoid misinterpretation as a shell comment character. 🙈

~| command — Pipe the message text through the specified filter command. If the command gives no output or terminates abnormally, retain the original text of the message. The command fmt(1) is often used as a rejustifying filter. iconic tool, honestly. 💅

If the first character of the command is a vertical bar, then the entire message including header fields is subject to the filter command, so ~|| echo Fcc: /tmp/test; cat will prepend a file-carbon-copy message header. Also see ~e, ~v. 🎀

~^ cmd [subcmd [arg3 [arg4]]] — A low-level compose mode command which shares semantics with digmsg, and therefore evaluates its command line as documented in “Shell-style argument quoting”. Does not manage the error number ! and the exit status ?: errors are handled via the protocol, and hard errors like I/O failures cannot be handled. 💀

The protocol consists of command lines followed by (a) response line(s). The first field of the response line represents a status code which specifies whether a command was successful or not, whether result data is to be expected, and if so, the format of the result data. Response data will be shell quoted as necessary for consumption by readsh, or eval and vpospar, to name a few. Error status code lines may optionally contain additional context. okay so here's the code chart, bestie: 📊

210 — Status ok; the remains of the line are the result.
211 — Status ok; the rest of the line is optionally used for more status. What follows are lines of result addresses, terminated by an empty line. All the input, including the empty line, must be consumed before further commands can be issued. Address lines consist of two tokens: first the plain network address, e.g. bob@exam.ple, followed by the (quoted) full address as known: '(Lovely) Bob <bob@exam.ple>'. Non-network addresses use the first field to indicate the type (hyphen-minus - for files, vertical bar | for pipes, and number sign # for names which will undergo alias processing) instead, and the actual value will be in the second field. 🌈
212 — Status ok; the rest of the line is optionally used for more status. What follows are lines of furtherly unspecified (quoted) string content, terminated by an empty line. All the input, including the empty line, must be consumed before further commands can be issued.
500 — Syntax error; invalid command.
501 — Syntax error in parameters or arguments.
505 — Error: an argument fails verification. For example an invalid address has been specified (also see expandaddr), or an attempt was made to modify anything in S-nail's own namespace, or a modifying subcommand has been used on a read-only message. 🚫
506 — Error: an otherwise valid argument is rendered invalid due to context. For example, a second address is added to a header which may consist of a single address only.

If a command indicates failure then the message will have remained unmodified. Most commands can fail with 500 if required arguments are missing, or excessive arguments have been given (false command usage). ([v15 behaviour may differ] The latter does not yet occur regularly, because as stated in “Shell-style argument quoting” our argument parser is not yet smart enough to work on subcommand base; for example one might get excess argument error for a three argument subcommand that receives four arguments, but not for a four argument subcommand which receives six arguments: here excess will be joined. 💀) The following (case-insensitive) commands are supported:

attachment — This command allows listing, removal and addition of message attachments. The second argument specifies the subcommand to apply, one of:
- attribute — This uses the same search mechanism as described for remove and prints any known attributes of the first found attachment via 212 upon success or 501 if no such attachment can be found. The attributes are written as lines with a keyword and a value token. ⭐
- attribute-at — This uses the same search mechanism as described for remove-at and is otherwise identical to attribute.
- attribute-set — This uses the same search mechanism as described for remove, and will set the attribute given as the fourth to the value given as the fifth token argument. If the value is an empty token, then the given attribute is removed, or reset to a default value if existence of the attribute is crucial. 💅

It returns via 210 upon success, with the index of the found attachment following, 505 for message attachments or if the given keyword is invalid, and 501 if no such attachment can be found. The following keywords may be used (case-insensitively):

'filename' — sets the filename of the MIME part, aka the name that gets used for display and when (suggesting a name for) saving (purposes). 💾
'content-description' — associates some descriptive info with the attachment's content; some MUAs will use this instead of the plain filename, so bestie, use it wisely. ✨
'content-id' — may be used to uniquely identify MIME entities in several contexts. Heads up though: this one expects a special reference address format as defined in RFC 2045, and it generates a 505 when the address content verification fails. 😭
'content-type' — defines the media type/subtype of the part, which is managed automatically, but like… you can overwrite it. main character energy.
'content-disposition' — automatically set to the string 'attachment'. Periodt, no notes.

attribute-set-at — this one uses the exact same search mechanism as described for remove-at, and is otherwise identical to attribute-set. literally the same vibe, different address.

insert — adds the attachment given as the third argument, specified exactly as documented for the command line option -a, and it supports the message number extension as documented for ~@. On success it reports 210, with the index of the new attachment right after it 🎀. It reports 505 if the given file can't be opened, 506 if an on-the-fly character set conversion fails, and otherwise 501. Oh and 501 also shows up if character set conversion is requested but not available. rude but okay.

list — lists all attachments via 212, or reports 501 if there are no attachments at all. Fun fact: this is the default command of attachment when no second argument has been given. 💅

remove — removes the attachment given as the third argument, reporting 210 on success or 501 if no such attachment can be found. Here's the tea on how it matches:

If there's any path component in the given argument, then an exact match of the path that was used to create the attachment is used directly.
But if only the basename of that path matches, then all attachments get traversed to find an exact match first, and the removal happens afterwards. If multiple basenames match? 506 error, babes. 💀
Message attachments are treated as absolute pathnames.

If there's no path component in the given argument, then all attachments get searched for filename= parameter matches as well as for matches of the basename of the path that was used when the attachment was created. Multiple matches result in a 506. 🙈

remove-at — interprets the third argument as a number and removes the attachment at that list position (counting from one!), reporting 210 on success, or 505 if the argument isn't a number, or 501 if no such attachment exists. yes, one-based, we don't make the rules.

header — this command lets you list, inspect, and edit message headers. 🎀 Quick note: header name case is not normalized, so use case-insensitive comparison when matching names. The second argument picks the subcommand, one of:

insert — creates a new or additional instance of the header given in the third argument, with the header body content given as the fourth token. It may return:

501 if the third argument specifies a free-form header field name that's invalid, or if body content extraction fails to succeed
505 if any extracted address doesn't pass syntax and/or security checks, or on S-nail namespace violations
506 to indicate prevention of excessing a single-instance header — and note that Subject: can be appended to (a space separator gets added automatically first, bless)

To:, Cc: and Bcc: support the ?single modifier to enforce treatment as a single addressee, like for example header insert To?single: 'exa, <m@ple>'; the word single is optional. 🦋

On success 210 is returned, followed by the name of the header and the list position of the newly inserted instance. The list position is always 1 for single-instance header fields. All free-form header fields are managed in a single list; also see customhdr. ✨

list — without a third argument you get a list of all yet-existing headers via 210. This is the default command of header if no second argument has been given. A third argument restricts output to just that header, which may fail with 501 if no such field is defined. 👑

remove — removes all instances of the header given as the third argument, reporting 210 on success, 501 if no such header can be found, and 505 on S-nail namespace violations. no cap.

remove-at — removes from the header given as the third argument the instance at the list position (counting from one!) given with the fourth argument, reporting 210 on success, or 505 if the list position argument isn't a number or on S-nail namespace violations, and 501 if no such header instance exists. 🌸

show — shows the content of the header given as the third argument. Depending on the header type this may respond with 211 or 212; any failure results in 501.

In compose-mode, read-only access to optional pseudo headers in the S-nail private namespace is available:

'Mailx-Command:' — the name of the command that generates the message, one of forward, Lreply, mail, Reply, reply, resend. This pseudo header always exists (in compose-mode). 💖
'Mailx-Raw-To:', 'Mailx-Raw-Cc:', 'Mailx-Raw-Bcc:' — represent the frozen initial state of these headers before any transformation (alias, alternates, recipients-in-cc etc.) took place. 🧊
'Mailx-Orig-Sender:', 'Mailx-Orig-From:', 'Mailx-Orig-To:', 'Mailx-Orig-Cc:', 'Mailx-Orig-Bcc:' — the values of said headers of the original message that has been addressed by any of reply, forward, resend. The sender field is special: it gets filled in with the sole sender according to RFC 5322 rules, so it may thus be equal to the from field. iykyk.

help, ? — shows an abstract of the above commands via 211. your little cheat sheet, bestie 🫶

version — prints the protocol version via 210. iconic, brief, slays.

~A — the same as ~i Sign. ⭐

~a — the same as ~i sign. (lowercase, different vibe, same energy)

~b name ... — adds the given names to the list of blind carbon copy recipients. 🤫

~c name ... — adds the given names to the list of carbon copy recipients. 💌

~d — reads the file specified by the DEAD variable into the message. dramatic name, useful feature. 💀

~e — fires up your TEXT EDITOR on the message you've collected so far, then drops you right back into compose mode 💅 (there's also ~v if you want a more display-oriented editor, and ~|| gives you a whole pipe-based editing situation, iykyk)
~F messages — reads the named messages into the message you're sending, and it's generous about it: all message headers and MIME parts come along for the ride, honouring forward-add-cc as well as forward-inject-head and forward-inject-tail. No messages specified? Then it reads in the current message, aka the “dot” ✨
~f messages — also reads the named messages into the message being sent, and if you don't name any it grabs the current message, the “dot”. But this one is picky in a different way: it strips down the list of header fields according to the ‘forward’ white- and blacklist selection of headerpick (with posix: the ‘type’ selection instead), and it honours forward-add-cc as well as forward-inject-head and forward-inject-tail. For MIME multipart messages, only the first displayable part is included 🎀
~H — in interactive mode, edits the message header fields ‘From:’, ‘Reply-To:’ and ‘Sender:’ by typing each one in turn and letting you edit the field. The default values for these fields originate from the from, reply-to and sender variables. In non-interactive mode this sets ^ERR-NOTTY 🙈
~h — same energy, different fields: in interactive mode it edits ‘To:’, ‘Cc:’, ‘Bcc:’ and ‘Subject:’ by typing each one in turn and letting you edit the field. In non-interactive mode this sets ^ERR-NOTTY, no cap
~I variable — inserts the value of the specified variable into the message. The message stays completely unaltered if the variable is unset or empty (respectful king 👑). Any embedded character sequences \t horizontal tabulator and \n line feed are expanded in posix mode; otherwise the expansion should occur at set time ([v15 behaviour may differ] by using the command modifier wysh)
~i variable — literally like ~I, but it appends a newline character. That's it. That's the whole bit 💖
~M messages — reads the named messages into the message being sent, indented by indentprefix. If no messages are specified, it reads the current message, the “dot”. Honours forward-add-cc as well as forward-inject-head and forward-inject-tail
~m messages — reads the named messages into the message being sent, indented by indentprefix, and if none are named it takes the current message, the “dot”. Strips down the list of header fields according to the ‘type’ white- and blacklist selection of headerpick. Honours forward-add-cc as well as forward-inject-head and forward-inject-tail. For MIME multipart messages, only the first displayable part is included 🌸
~p — displays the message collected so far, prefaced by the message header fields and followed by the attachment list, if any. A lil preview moment ✨
~Q — reads in the given / current message(s) using the algorithm of quote (except that it is implicitly assumed, even if not set), honouring quote-add-cc
~q — aborts the message being sent, copying it to the file specified by the DEAD variable if save is set 💀
~R filename — identical to ~r, but indents each line that has been read by indentprefix
~r filename [HERE-delimiter] — reads the named file into the message, object to “Filename transformations”, excluding shell globs and variable expansions. If filename is the hyphen-minus - then standard input is used (for pasting, for example). Only in this latter mode may HERE-delimiter be given: if it is, data will be read in until the given HERE-delimiter is seen on a line by itself, and encountering EOF is an error. The HERE-delimiter is a required argument in non-interactive mode; if it is single-quote quoted then the pasted content will not be expanded, [v15 behaviour may differ] otherwise a future version of S-nail may perform shell-style expansion on the content 🦋
~s string — causes the named string to become the current subject field. Newline (NL) and carriage-return (CR) bytes are invalid and will be normalized to space (SP) characters. Bestie cannot have you smuggling line breaks into your Subject, sorry 🎀
~t name ... — adds the given name(s) to the direct recipient list
~U messages — reads in the given / current message(s), excluding all headers, indented by indentprefix. Honours forward-add-cc as well as forward-inject-head and forward-inject-tail
~u messages — reads in the given / current message(s), excluding all headers. Honours forward-add-cc as well as forward-inject-head and forward-inject-tail
~v — invokes the VISUAL editor on the message collected so far, then returns to compose mode. ~e is the move for a less display-oriented editor, and ~|| offers a pipe-based editing approach 🌈
~w filename — writes the message onto the named file, which is object to the usual “Filename transformations”. If the file exists, the message is appended to it 🔥
~x — same as ~q, except that the message is not saved at all. Gone. Deleted. Poof 💀

✨ INTERNAL VARIABLES ✨

Okay so internal S-nail variables are controlled via the set and unset commands, and here's the cute trick: prefixing a variable name with the string ‘no’ and calling set has the exact same effect as using unset — unset crt and set nocrt do the same thing, periodt 💅 varshow will give more insight on the given variable(s), and set, when called without arguments, will show a listing of all variables. Both commands support a more verbose listing mode. Some well-known variables will also become inherited from the program “ENVIRONMENT” implicitly, others can be imported explicitly with the command environ and henceforth share said properties.

Two different kinds of internal variables exist, and both of which can also form chains 🧚 There are boolean variables, which can only be in one of the two states “set” and “unset”, and value variables with a(n optional) string value. For the latter, proper quoting is necessary at assignment time — the introduction of the section “COMMANDS” documents the supported quoting rules.

? wysh set one=val\ 1 two="val 2" \
    three='val "3"' four=$'val \'4\''; \
    varshow one two three four; \
    unset one two three four

Dependent upon the actual option, string values may become interpreted as colour names, command specifications, normal text, etc. They may be treated as numbers, in which case decimal values are expected if so documented, but otherwise any numeric format and base that is valid and understood by the vexpr command may be used, too 👑

There also exists a special kind of string value, the “boolean string”, which must either be a decimal integer (in which case ‘0’ is false and ‘1’ and any other value is true) or any of the (case-insensitive) strings ‘off’, ‘no’, ‘n’ and ‘false’ for a false boolean and ‘on’, ‘yes’, ‘y’ and ‘true’ for a true boolean. A special kind of boolean string is the “quadoption”: it can optionally be prefixed with the (case-insensitive) term ‘ask-’, as in ‘ask-yes’. In interactive mode the user will be prompted, otherwise the actual boolean is used ⭐

Variable chains extend a plain ‘variable’ with ‘variable-HOST’ and ‘variable-USER@HOST’ variants. Here ‘HOST’ will be converted to all lowercase when looked up (but not when the variable is set or unset!), [Option]ally IDNA converted, and indeed means ‘server:port’ if a ‘port’ had been specified in the contextual Uniform Resource Locator URL. See “On URL syntax and credential lookup”. Even though this mechanism is based on URLs, no URL percent encoding may be applied to neither of ‘USER’ nor ‘HOST’ — variable chains need to be specified using raw data, and the mentioned section contains examples. Variables which support chains are explicitly documented as such, and S-nail treats the base name of any such variable special, meaning that users should not create custom names like ‘variable-xyz’ in order to avoid false classifications and treatment of such variables 🙈

Okay bestie, listen: don't go inventing your own -something variable names. That's how you end up classified as something you're not, and nobody wants that 💀

🎀 Initial settings 🎀

The standard POSIX 2008/Cor 2-2016 mandates the following initial variable settings: noallnet, noappend, asksub, noaskbcc, noautoprint, nobang, nocmd, nocrt, nodebug, nodot, escape set to ~, noflipr, nofolder, header, nohold, noignore, noignoreeof, nokeep, nokeepsave, nometoo, nooutfolder, nopage, prompt set to ? , noquiet, norecord, save, nosendwait, noshowto, noSign, nosign, toplines set to 5.

However, S-nail has built-in some initial (and some default) settings which (may) diverge, others may become adjusted by one of the “Resource files”. Displaying the former is accomplished via set:

$ s-nail -:/ -v -Xset -Xx

In general this implementation sets (and has extended the meaning of) sendwait, and does not support the noonehop variable — use command line options or mta-arguments to pass options through to a mta. The default global resource file sets, among others, the variables hold, keep and keepsave, establishes a default headerpick selection etc., and should thus be taken into account 🔥

🦋 Variables 🦋

? — (Read-only) The exit status of the last command, or the return value of the macro called last. This status has a meaning in the state machine: in conjunction with errexit any non-0 exit status will cause a program exit, and in posix mode any error while loading (any of the) resource files will have the same effect. ignerr, one of the “Command modifiers”, can be used to instruct the state machine to ignore errors 👑
! — (Read-only) The current error number (errno(3)), which is set after an error occurred; it is also available via ^ERR, and the error name and documentation string can be queried via ^ERRNAME and ^ERRDOC. [v15 behaviour may differ] This machinery is new and the error number is only really usable if a command explicitly states that it manages the variable !, for others errno will be used in case of errors, or ^ERR-INVAL if that is 0: it thus may or may not reflect the real error. The error number may be set with the command return 💅
^ — (Read-only) bestie this is a multiplexer variable ✨ it does dynamic expansion of whatever state or condition you ask for. The options are:
- ^ERR, ^ERRDOC, ^ERRNAME — the number, the documentation, and the name of the current errno(3), respectively — and yeah, these usually get set right after an error happened 💀 The documentation is an [Option], and the name gets used if the doc isn't available. [v15 behaviour may differ] This whole machinery is new, and it's usually only reliable if a command explicitly says it manages the variable !, which is effectively identical to ^ERR. Ngl each of these can be suffixed with a hyphen minus followed by a name or number, and then the expansion refers to that given error 👑 Also heads up: this is a direct mapping of (a subset of) the system error values:

define work {
  eval echo \$1: \$^ERR-$1:\
    \$^ERRNAME-$1: \$^ERRDOC-$1
  vput vexpr i + "$1" 1
  if [ $i -lt 16 ]
    \xcall work $i
  end
}
call work 0

^ERRQUEUE-COUNT, ^ERRQUEUE-EXISTS — the number of messages sitting in the [Option]al log queue of errors, and a boolean saying whether that queue is not empty, respectively 🎀 Both of these are always 0 unless features includes ,+errors,.

* — (Read-only) expands all positional parameters (see 1), separated by the first character of the value of ifs. [v15 behaviour may differ] The special semantics of the equally named special parameter of sh(1) are not yet supported 🙈
@ — (Read-only) expands all positional parameters (see 1), separated by a space character. And if you put it inside double quotation marks, each positional parameter is properly quoted so it expands back into a single parameter again 💅 slay.
# — (Read-only) expands to the number of positional parameters, i.e., the size of the positional parameter stack, in decimal 🔢
0 — (Read-only) Inside the scope of a defined and called macro, this expands to the name of the calling macro — or to the empty string if the macro is running from top-level. For the [Option]al regular expression search and replace operator of vexpr, this expands to the entire matching expression 🌸 It represents the program name in global context.
1 — (Read-only) Access of the positional parameter stack. All the further parameters can be accessed with this syntax too — 2, 3, etc. — and positional parameters can be shifted off the stack by calling shift. The parameter stack contains, like, the arguments of a called defined macro, the matching groups of the [Option]al regular expression search and replace expression of vexpr, and it can be explicitly created or overwritten with the command vpospar ✨
account — (Read-only) is set to the active account 🫶
add-file-recipients — (Boolean) When file or pipe recipients have been specified, mention them in the corresponding address fields of the message instead of silently stripping them from their recipient list. By default such addressees are not mentioned 🤫
allnet — (Boolean) Causes only the local part to be evaluated when comparing addresses.
append — (Boolean) Causes messages saved in the “secondary mailbox” MBOX to be appended to the end rather than prepended. Bestie, this should always be set 👑
askatend — (Boolean) Causes the prompts for Cc: and Bcc: lists to appear after the message has been edited.
askattach — (Boolean) If set, S-nail asks an interactive user for files to attach at the end of each message; an empty line finalizes the list 📎
askcc — (Boolean) Causes the interactive user to be prompted for carbon copy recipients (at the end of each message if askatend or bsdcompat are set).
askbcc — (Boolean) Causes the interactive user to be prompted for blind carbon copy recipients (at the end of each message if askatend or bsdcompat are set).
asksend — (Boolean) Causes the interactive user to be prompted for confirmation to send the message, or to reenter compose mode, after having been shown a preliminary envelope summary 💌
asksign — (Boolean)[Option] Causes the interactive user to be prompted if the message is to be signed at the end of each message. The smime-sign variable is ignored when this variable is set 👀
asksub — (Boolean) Causes S-nail to prompt the interactive user for the subject upon entering compose mode — unless a subject already exists.
attrlist — a sequence of characters to display in the attribute column of the headline as shown in the display of headers 🎀 Each one is for one type of message (see “Message states”), with the default being NUROSPMFAT+-$~ — or NU *HMFAT+-$~ if the bsdflags variable is set — in the following order:
- N — new.
- U — unread but old.
- R — new but read.
- O — read and old.
- S — saved.
- P — preserved.
- M — mboxed.
- F — flagged.
- A — answered.
- T — draft.
- + — [v15 behaviour may differ] start of a (collapsed) thread in threaded mode (see autosort, thread);
- - — [v15 behaviour may differ] an uncollapsed thread in threaded mode; only used in conjunction with -L.
- $ — classified as spam 💀
- ~ — classified as possible spam 🙈
autobcc — Specifies a list of recipients to which a blind carbon copy of each outgoing message will be sent automatically.
autocc — Specifies a list of recipients to which a carbon copy of each outgoing message will be sent automatically ✨
autocollapse — (Boolean) Causes threads to be collapsed automatically when threaded sort mode is entered (see the collapse command).
autoprint — (Boolean) Enable automatic typeing of a(n existing) “successive” message after delete and undelete commands — the message that becomes the new “dot” is shown automatically, as via dp or dt 👑
autosort — Causes sorted mode (see the sort command) to be entered automatically, with the value of this variable as sorting method, when a folder is opened — for example set autosort=thread 🦋
bang — (Boolean) Enables the substitution of all not-(reverse-solidus)-escaped exclamation mark ! characters by the contents of the last executed command, for the ! shell escape command and ~!, one of the compose mode “COMMAND ESCAPES”. If this variable is not set, no reverse solidus stripping is performed 💅
bind-timeout — [Obsolete] Predecessor of bind-inter-byte-timeout. [v15 behaviour may differ] Setting this automatically sets the successor.
bind-inter-byte-timeout — [Option] Terminals may generate multi-byte sequences for special function keys, for example — but these sequences may not become read as a unit 😭 And multi-byte sequences can be defined freely via bind. This variable specifies the timeout in milliseconds that the MLE (see “On terminal control and line editor”) waits for more bytes to arrive, unless it considers a sequence “complete”. The default is 200, the maximum is about 10 seconds ⏱️ In the following example, the comments state which sequences are affected by this timeout:

? bind base abc echo 0 # abc
? bind base ab,c echo 1 # ab
? bind base abc,d echo 2 # abc
? bind base ac,d echo 3 # ac
? bind base a,b,c echo 4
? bind base a,b,c,d echo 5
? bind base a,b,cc,dd echo 6 # cc and dd

bind-inter-key-timeout — [Option] Multi-key bind sequences do not time out by default. If this variable is set, then the current key sequence is forcefully terminated once the timeout (in milliseconds) triggers 🫶 The value should be (maybe significantly) larger than bind-inter-byte-timeout, but may not excess the maximum, too.
bsdcompat — (Boolean) Sets some cosmetical features to traditional BSD style; has the same affect as setting askatend and all other variables prefixed with bsd; it also changes the behaviour of emptystart (which does not exist in BSD) 💀
bsdflags — (Boolean) Changes the letters shown in the first column of a header summary to traditional BSD style.
bsdheadline — (Boolean) Changes the display of columns in a header summary to traditional BSD style.
bsdmsgs — (Boolean) Changes some informational messages to traditional BSD style.
bsdorder — (Boolean) Causes the Subject: field to appear immediately after the To: field in message headers and with the ~h “COMMAND ESCAPES”.
build-cc, build-ld, build-os, build-rest — (Read-only) The build environment 🛠️ including the compiler, the linker, the operating system S-nail has been build for — usually taken from uname(1) via uname -s, and then lowercased — as well as all the possibly interesting rest of the configuration and build environment. This information is also available in the verbose output of the command version ⭐
charset-7bit — The value that should appear in the charset= parameter of Content-Type: MIME header fields when no character set conversion of the message data was performed. This defaults to US-ASCII, and the chosen character set should be US-ASCII compatible 🌈

`charset-8bit`

[Option] The default 8-bit character set, bestie — the one that gets used as an implicit last member of the variable sendcharsets. ✨

So like, defaults? It's UTF-8 if character set conversion capabilities are available, and ISO-8859-1 otherwise (unless the operating system environment is known to always and exclusively support UTF-8 locales) — in which case the only supported character set is ttycharset and this variable is effectively ignored. Slay, but also 😭.

`charset-unknown-8bit`

[Option] OK so RFC 1428 specifies conditions when internet mail gateways shall "upgrade" the content of a mail message by using a character set with the name unknown-8bit. Because of the unclassified nature of this character set, S-nail will not be capable of converting this character set to any other character set. 💀

If this variable is set, any message part which uses the character set unknown-8bit is assumed to really be in the character set given in the value — otherwise the (final) value of charset-8bit is used for this purpose.

This variable will also be taken into account if a MIME type (see "The mime.types files") of a MIME message part that uses the binary character set is forcefully treated as text. 🫶

`cmd`

The default value for the pipe command.

`colour-disable`

(Boolean)[Option] Forcefully disable usage of colours. Also see the section "Coloured display". (Sad but valid 💅)

`colour-pager`

(Boolean)[Option] Whether colour shall be used for output that is paged through PAGER. Heads up though — pagers may need special command line options, for example less(1) requires the option -R and lv(1) the option -c in order to support colours. 🌈

Often doing manual adjustments is unnecessary since S-nail may perform adjustments dependent on the value of the environment variable PAGER (see there for more).

`contact-mail`, `contact-web`

(Read-only) Addresses for contact per email and web, respectively, for bug reports, suggestions, or anything else regarding S-nail. 🎀 The former can be used directly: ? eval mail $contact-mail

`content-description-forwarded-message`, `content-description-quote-attachment`, `content-description-smime-message`, `content-description-smime-signature`

[Option](partially) Strings which will be placed in according Content-Description: headers if non-empty. They all have default values, for example Forwarded message. ✨

`crt`

In a(n interactive) terminal session, then if this valued variable is set it will be used as a threshold to determine how many lines the given output has to span before it will be displayed via the configured PAGER. Usage of the PAGER can be forced by setting this to the value 0; setting it without a value will deduce the current height of the terminal screen to compute the threshold (see LINES, screen and stty(1)).

[v15 behaviour may differ] At the moment this uses the count of lines of the message in wire format, which, dependent on the mime-encoding of the message, is unrelated to the number of display lines. (The software is old and historically the relation was a given thing.) 😭

`customhdr`

Define a set of custom headers to be injected into newly composed or forwarded messages. A custom header consists of the field name followed by a colon : and the field content body. Standard header field names cannot be overwritten by a custom header, with the exception of Comments: and Keywords:. 👑

Different to the command line option -C the variable value is interpreted as a comma-separated list of custom headers: to include commas in header bodies they need to become escaped with reverse solidus \. Headers can be managed more freely in "Compose mode" via ~^.

? set customhdr='Hdr1: Body1-1\, Body1-2, Hdr2: Body2'

`datefield`

Controls the appearance of the %d date and time format specification of the headline variable, that is used, for example, when viewing the summary of headers. If unset, then the local receiving date is used and displayed unformatted — otherwise the message sending Date:. 🕰️

It is possible to assign a strftime(3) format string and control formatting, but embedding newlines via the %n format is not supported, and will result in display errors. The default is %Y-%m-%d %H:%M, and also see datefield-markout-older.

`datefield-markout-older`

Only used in conjunction with datefield. Can be used to create a visible distinction of messages dated more than a day in the future, or older than six months — a concept comparable to the -l option of the POSIX utility ls(1). 🦋

If set to the empty string, then the plain month, day and year of the Date: will be displayed, but a strftime(3) format string to control formatting can be assigned. The default is %Y-%m-%d.

`debug`

(Boolean) (Almost) enter a debug-only sandbox mode which generates many log messages, disables the actual delivery of messages, and also implies norecord as well as nosave. Also see verbose. 🔥

Lowkey the sandbox where nothing actually ships. fr fr.

`disposition-notification-send`

(Boolean)[Option] Emit a Disposition-Notification-To: header (RFC 3798) with the message. This requires the from variable to be set. ✨

`dot`

(Boolean) When dot is set, a period . on a line by itself during message input in (interactive or batch -#) "Compose mode" will be treated as end-of-message (in addition to the normal end-of-file condition). 🎀

This behaviour is implied in posix mode with a set ignoreeof.

`dotlock-disable`

(Boolean)[Option] Disable creation of "dotlock files" for MBOX databases.

`dotlock-ignore-error`

[Obsolete](Boolean)[Option] Ignore failures when creating "dotlock files". Please use dotlock-disable instead. 👑

`editalong`

If this variable is set then the editor is started automatically when a message is composed in interactive mode. If the value starts with the letter v then this acts as if ~v, otherwise as if ~e (see "COMMAND ESCAPES") had been specified. 💅

The editheaders variable is implied for this automatically spawned editor session.

`editheaders`

(Boolean) When a message is edited while being composed, its header is included in the editable text.

`emptystart`

(Boolean) When entering interactive mode S-nail normally writes No mail for user and exits immediately if a mailbox is empty or does not exist. If this variable is set S-nail starts even with an empty or non-existent mailbox (the latter behaviour furtherly depends upon bsdcompat, though). 🌸

`errexit`

(Boolean) Let each command with a non-0 exit status, including every called macro which returns a non-0 status, cause a program exit unless prefixed by ignerr (see "Command modifiers"). 😭 This also affects "COMMAND ESCAPES", but which use a different modifier for ignoring the error. Please refer to the variable ? for more on this topic.

`errors-limit`

[Option] Maximum number of entries in the errors queue.

`escape`

The first character of this value defines the escape character for "COMMAND ESCAPES" in "Compose mode". The default value is the character tilde ~. If set to the empty string, command escapes are disabled. 💜

`expandaddr`

If unset only user name and email address recipients are allowed "On sending mail, and non-interactive mode". If set without value all possible recipient types will be accepted. 🌈

A value is parsed as a comma-separated list of case-insensitive strings, and if that contains restrict behaviour equals the former except when in interactive mode or if "COMMAND ESCAPES" were enabled via -~ or -#, in which case it equals the latter, allowing all address types. restrict really acts like restrict,-all,+name,+addr, so care for ordering issues must be taken. ⚠️

Recipient types can be added and removed with a plus sign + or hyphen-minus - prefix, respectively. By default invalid or disallowed types are filtered out and cause a warning, hard send errors need to be enforced by including fail. The value all covers all types, fcc whitelists Fcc: header targets regardless of other settings, file file targets (it includes fcc), pipe command pipeline targets, name user names still unexpanded after alias and mta-aliases processing and thus left for expansion by the mta (invalid for the built-in SMTP one), and addr network addresses.

Targets are interpreted in the given order, so that restrict,fail,+file,-all,+addr will cause hard errors for any non-network address recipient address unless running interactively or having been started with the option -~ or -#; in the latter case(s) any type may be used. 👑

User-name receivers that address valid local users can be expanded into fully qualified network addresses (also peep hostname, bestie) by sticking <code>nametoaddr</code> in the list. Back in the day invalid recipients just got silently stripped off — no errors, no drama — and you can change that by making <code>failinvaddr</code> an entry of the list (it genuinely acts like <code>failinvaddr,+addr</code>). Same vibe with <code>domaincheck</code> (really <code>domaincheck,+addr</code>): it compares address domain names against a whitelist and strips off (and gives <code>fail</code> for hard errors) any addressee that flunks the test 💅. The domain name <code>localhost</code> and the non-empty value of hostname (the real hostname otherwise) are always whitelisted, and expandaddr-domaincheck is there if you wanna extend that list.

Finally, some address providers (looking at you -b, -c, and literally all the other command line recipients) get evaluated as if they were specified inside dollar-single-quotes (see “Shell-style argument quoting”) when the value list contains the string <code>shquote</code>. iykyk 🫶

expandaddr-domaincheck — you can set this to a comma-separated list of domain names that should be whitelisted when the <code>domaincheck</code> mode of expandaddr gets evaluated. Heads up: IDNA encoding is not done automatically, so use addrcodec to prep the domain (of an address). 🎀
expandargv — unless this variable is set, extra mta (Mail-Transfer-Agent) arguments from the command line — the kind you pass after a -- separator — make the program terminate with a failure status. You can get the exact same strictness by using the special (case-insensitive) value <code>fail</code>. There's a chiller variant: <code>restrict</code>, otherwise identical, which does accept those arguments in interactive mode, or if tilde commands were explicitly enabled with one of the command line options -~ or -#. The empty value allows unconditional usage, no cap. ✨
features — (Read-only) A string handing you a list of optional features. Each feature gets a plus sign + in front if it's available, or a hyphen-minus - if it's not. To make substring matching easier, the string starts and ends with a comma. The output of the version command shows this same info in a much more pleasant form. 👑
flipr — (Boolean) This one reverses the meanings of a set of reply commands. It turns the lowercase variants, which by default address all recipients in the message header (reply, respond, followup), into the uppercase variants, which by default address the sender only (Reply, Respond, Followup) — and vice versa. Flip it and slay. 🔄
folder — the default path where mailboxes get saved: filenames starting with the plus sign + get that plus swapped for the value of this variable if it's set — otherwise the plus sign just stays put when doing “Filename transformations”. Also see folder for more on this topic, and know about the standard imposed implications of outfolder. The value itself supports a subset of transformations, and if the non-empty value doesn't start with a solidus /, then HOME gets prefixed automatically. Once the actual value is evaluated, the internal variable folder-resolved gets updated for caching purposes. 🗂️
folder-hook-FOLDER, folder-hook — names a defined macro that gets called whenever a folder is opened. The macro also fires when new mail arrives, but message lists for commands executed from the macro then only include the newly arrived messages. localopts are activated by default in a folder hook, which means the covered settings get reverted once you leave the folder again. 🦋

The specialized form overrides the generic one if <code>FOLDER</code> matches the file being opened. Unlike other folder specifications, the fully expanded name of the folder — no metacharacters — is used, to avoid ambiguities. However, if the mailbox lives under folder, then the usual + specification gets tried in addition. So if folder is <code>mail</code> (and therefore relative to the user's home directory), then /home/usr1/mail/sent will be tried as <code>folder-hook-/home/usr1/mail/sent</code> first, followed by <code>folder-hook-+sent</code>. Cute, right? 💖

folder-resolved — (Read-only) Set to the fully resolved path of folder once that evaluation has happened; rather internal. 🙈
followup-to — (Boolean) Controls whether a Mail-Followup-To: header is generated when you send messages to known mailing lists. The user — as determined via from (or, if that contains multiple addresses, sender) — gets placed in there if any list addressee is not a subscribed list. Also see followup-to-honour and the commands mlist, mlsubscribe, reply and Lreply. 📬
followup-to-add-cc — (Boolean) Controls whether the user gets added to the messages' Cc: list in addition to placing an entry in Mail-Followup-To: (see followup-to). Two for one. 🎀
followup-to-honour — controls whether a Mail-Followup-To: header is honoured when group-replying to a message via reply or Lreply. This one's a “quadoption” — if you set it without a value it defaults to “yes”. And see followup-to. ✅
forward-add-cc — (Boolean) Whether senders of messages forwarded via ~F, ~f, ~m, ~U or ~u shall be made members of the carbon copies Cc: list. 🌸
forward-as-attachment — (Boolean) Original messages normally get sent as inline text with the forward command, and only the first part of a multipart message is included. Flip this setting on and messages get sent as unmodified MIME message/rfc822 attachments with all their parts included. Iconic behaviour, honestly. 🔥
forward-inject-head, forward-inject-tail — the strings to put before and after the text of a message with the forward command, respectively. The former defaults to <code>-------- Original Message --------\n</code>. Special format directives in these strings get expanded if possible, and if so configured the output gets folded according to quote-fold; for more deets please refer to quote-inject-head. Heads up though: injections will not be performed by forward if the variable forward-as-attachment is set — but the “COMMAND ESCAPES” ~F, ~f, ~M, ~m, ~U, ~u always inject. 💌
from — the address (or a list of addresses) to put into the From: field of the message header. Quoting RFC 5322: the author(s) of the message, that is, the mailbox(es) of the person(s) or system(s) responsible for the writing of the message. According to that RFC, setting the sender variable is required if from contains more than one address. [v15 behaviour may differ] Please expect automatic management of the from and sender relationship. Dependent on the context, these addresses are handled as if they were in the list of alternates. 📇

If a file-based MTA is used, then from (or, if that contains multiple addresses, sender) can nonetheless be used as the envelope sender address at the MTA protocol level (the RFC 5321 reverse-path) — either via the -r command line option (without argument; see there for more), or by setting r-option-implicit.

If the machine's hostname isn't valid at the Internet (dialup machine, we've all been there), then either this variable or hostname ([v15-compat] a SMTP-based mta adds even more fine-tuning capabilities with smtp-hostname) have to be set: if so, the message and MIME part related unique ID fields Message-ID: and Content-ID: will be created (except when disallowed by message-id-disable or stealthmua). 🛰️

fullnames — (Boolean) Due to historical reasons, comments and name parts of email addresses get removed by default when sending mail, replying to, or forwarding a message. Set this variable and that stripping does not happen. Names stay. Periodt. 💜
fwdheading — [Obsolete] Predecessor of forward-inject-head. That's it, that's the whole vibe. 💀
header — (Boolean) Causes the header summary to be written at startup and after commands that affect the number of messages or the order of messages in the current folder. Unless you're in posix mode, a header summary also shows up on folder changes. The command line option -N can be used to set noheader. 👀
headline — a format string to use for the summary of headers. Format specifiers in the given string start with a percent sign % and may be followed by an optional decimal number indicating the field width — and if that number is negative, the field is left-aligned. Names and addresses are subject to modifications according to showname and showto. Valid format specifiers are: ⭐
%% — a regular, plain percent sign. that's it, that's the whole job 🎀
%> — the "Dotmark". it's a space character, except on the current message (the "dot"), where it expands to >. this is dependent on headline-plain, bestie 👑
%< — also a "Dotmark": a space, but for the current message (the "dot") it expands to <. yep, same headline-plain dependency 💅
%$ — [Option] the spam score of the message, as classified via the command spamrate. lowkey crucial: if there's no spam support it shows only a replacement character. not me getting a placeholder 😭
%a — the message attribute character (the status flag!). the actual content can be adjusted by setting attrlist ✨
%d — the date found in the Date: header of the message when datefield is set (which is the default, obvi), otherwise it's the date when the message was received. formatting can be controlled by assigning a strftime(3) format string to datefield (and datefield-markout-older) 🗓️
%e — the indenting level in threaded sort mode. it's giving tree structure realness 🌳
%f — the address of the message sender 🫶
%i — the message thread tree structure. (note that this format does not support a field width, and it honours headline-plain) 🌸
%L — mailing list status: is the addressee of the message a known l (mlist) or L mlsubscribed mailing list? the letter P announces the presence of a RFC 2369 List-Post: header, which makes a message a valuable target of Lreply. iykyk 🔥
%l — the number of lines of the message, if available 📏
%m — the message number 🔢
%o — the number of octets (bytes) in the message, if available 💾
%S — the message subject (if any) in double quotes 🎀
%s — the message subject (if any) ✨
%t — the position in threaded/sorted order 📊
%U — the value 0 except in an IMAP mailbox, where it expands to the UID of the message 👑

The default is %>%a%m %-18f %16d %4l/%-5o %i%-s, or %>%a%m %20-f %16d %3l/%-5o %i%-S if bsdcompat is set. Also see attrlist, headline-plain and headline-bidi. no cap, that's the default and you should respect it 💖

`headline-bidi`

okay so bidirectional text needs special treatment when displaying headers, because numbers (in dates or for file sizes etc.) will not affect the current text direction, which in effect gives you ugly line layouts when arabic or other right-to-left text is to be displayed. like, it's giving chaos 🙈

on the other hand, only a minority of terminals is capable to correctly handle direction changes, so user interaction is necessary for acceptable results. note that extended host system support is required nonetheless — e.g., detection of the terminal character set is one precondition — and this feature only works in a Unicode (i.e., UTF-8) locale ⭐

in general, setting this variable will cause S-nail to encapsulate text fields that may occur when displaying headline (and some other fields, like dynamic expansions in prompt) with special Unicode control sequences. you can fine-tune the terminal support level by assigning a value:

no value (or any value other than 1, 2 and 3) will make S-nail assume that the terminal is capable to properly deal with Unicode version 6.3, in which case text is embedded in a pair of U+2068 (FIRST STRONG ISOLATE) and U+2069 (POP DIRECTIONAL ISOLATE) characters. in addition, no space on the line is reserved for these characters 💅
weaker support is chosen by using the value 1 (Unicode 6.3, but reserve the room of two spaces for writing the control sequences onto the line) 🦋
the values 2 and 3 select Unicode 1.1 support (U+200E, LEFT-TO-RIGHT MARK); the latter again reserves room for two spaces in addition 🌈

`headline-plain`

(Boolean) on Unicode (UTF-8) aware terminals, enhanced graphical symbols are used by default for certain entries of headline. if this variable is set, only basic US-ASCII symbols will be used. so: aesthetic mode off, plain mode on 🎀

`history-file`

[Option] the (expandable) location of a permanent history file for the MLE line editor ("On terminal control and line editor"). also see history-size 📜

`history-gabby`

[Option] add more entries to the MLE history as is normally done. a comma-separated list of case-insensitive strings can be used to fine-tune which gabby entries shall be allowed. if it contains errors, erroneous commands will also be added. all adds all optional entries, and is the fallback chattiness identifier of on-history-addition. she's chatty, she's iconic 💬

`history-gabby-persist`

(Boolean)[Option] the history-gabby entries will not be saved in persistent storage unless this variable is set. the knowledge of whether a persistent entry was gabby is not lost. also see history-file 💾

`history-size`

[Option] setting this variable imposes a limit on the number of concurrent history entries. if set to the value 0 then no further history entries will be added, and loading and incorporation of the history-file upon program startup can also be suppressed by doing this. runtime changes will not be reflected before the history is saved or loaded (again). read that twice, bestie 😭

`hold`

(Boolean) this setting controls whether messages are held in the system inbox, and it is set by default. yes, by default. periodt 👑

`hostname`

used instead of the value obtained from uname(3) and getaddrinfo(3) as the hostname when expanding local addresses — for example in From: (also see "On sending mail, and non-interactive mode", for expansion of addresses that have a valid user-, but no domain name in angle brackets) 🌸

if either of from or this variable is set, the message and MIME part related unique ID fields Message-ID: and Content-ID: will be created (except when disallowed by message-id-disable or stealthmua) ⭐

if the [Option]al IDNA support is available (see idna-disable), variable assignment is aborted when a necessary conversion fails 🙈

setting it to the empty string will cause the normal hostname to be used, but nonetheless enables creation of said ID fields. [v15-compat] in conjunction with the built-in SMTP mta smtp-hostname also influences the results: one should produce some test messages with the desired combination of hostname, and/or from, sender etc. first. test first, ask questions later 🫶

`idna-disable`

(Boolean)[Option] can be used to turn off the automatic conversion of domain names according to the rules of IDNA (internationalized domain names for applications). since the IDNA code assumes that domain names are specified with the ttycharset character set, an UTF-8 locale charset is required to represent all possible international domain names (before conversion, that is) 🌍

`ifs`

the input field separator that is used ([v15 behaviour may differ] by some functions) to determine where to split input data. okay, listen up, there are rules 👇

unsetting is treated as assigning the default value, \t\n 💅
if set to the empty value, no field splitting will be performed 🚫
if set to a non-empty value, all whitespace characters are extracted and assigned to the variable ifs-ws:
- ifs-ws will be ignored at the beginning and end of input. diverging from POSIX shells, default whitespace is removed in addition, which is owed to the entirely different line content extraction rules 🦋
- each occurrence of a character of ifs will cause field-splitting, any adjacent ifs-ws characters will be skipped ✂️

`ifs-ws`

(Read-only) automatically deduced from the whitespace characters in ifs. she's deduced, she's automatic, she's read-only ✨

`ignore`

(Boolean) ignore interrupt signals from the terminal while entering messages; instead echo them as @ characters and discard the current line. iconic behaviour honestly 🙈

`ignoreeof`

(Boolean) ignore end-of-file conditions (control-D) in "Compose mode" on message input and in interactive command input. if set, an interactive command input session can only be left by explicitly using one of the commands exit and quit, and message input in compose mode can only be terminated by entering a period . on a line by itself or by using the ~. "COMMAND ESCAPES"; setting this implies the behaviour that dot describes in posix mode. you're locked in, bestie 🔒

`inbox`

if this is set to a non-empty string it will specify the user's "primary system mailbox", overriding MAIL and the system-dependent default, and (thus) be used to replace % when doing "Filename transformations"; also see folder for more on this topic. the value supports a subset of transformations itself 💌

`indentprefix`

string used by the ~m, ~M and ~R "COMMAND ESCAPES" and by the quote option for indenting messages, in place of the POSIX mandated default tabulator character \t. also see quote-chars 🎀

keep (Boolean) — if you set this, an empty "primary system mailbox" file will not be removed. Heads up though: in conjunction with posix mode, any empty file will get removed unless this variable is set. Why do you care? It "may improve the interoperability with other mail user agents when using a common folder directory, and prevents malicious users from creating fake mailboxes in a world-writable spool directory." 💅 (v15 behaviour may differ) And scope check: only local regular (MBOX) files are covered here — Maildir and other mailbox types will never be removed, even if empty. 🫶
keep-content-length (Boolean) — when you're editing messages and writing MBOX mailbox files, S-nail can be told to keep the Content-Length: and Lines: header fields that some MUAs generate, just by setting this variable. Since S-nail does neither use nor update these non-standardized header fields (which in itself shows one of their conceptual problems, ngl), stripping them should increase interoperability in between MUAs that work with the same mailbox files. Note that if this is not set but writebackedited (as below) is, a possibly performed automatic stripping of these header fields already marks the message as being modified. (v15 behaviour may differ) At some future time S-nail will be capable to rewrite and apply an mime-encoding to modified messages, and then those fields will be stripped silently. ✨
keepsave (Boolean) — when a message is saved it's usually discarded from the originating folder when S-nail quits. This setting causes all saved message to be retained. lowkey a keeper 💖
line-editor-cpl-word-breaks [Option] — list of bytes which are used by the mle-complete tabulator completion to decide where word boundaries exist, by default "'@=;|: (v15 behaviour may differ) This mechanism is yet restricted. 🎀
line-editor-disable (Boolean) — turn off any line editing capabilities (from S-nail's POW, see "On terminal control and line editor" for more).
line-editor-no-defaults (Boolean) [Option] — do not establish any default key binding. Blank slate energy 🦋
log-prefix — error log message prefix string (s-nail: ).
mailbox-display (Read-only) — the name of the current mailbox (folder), possibly abbreviated for display purposes.
mailbox-resolved (Read-only) — the fully resolved path of the current mailbox. the receipts, literally 🔥
mailcap-disable (Boolean) [Option] — turn off consideration of MIME type handlers from, and implicit loading of, "The Mailcap files".
mailx-extra-rc — an additional startup file that is loaded as the last of the "Resource files". Use this file for commands that are not understood by other POSIX mailx(1) implementations, i.e., mostly anything which is not covered by "Initial settings". it's giving ✨exclusive club✨
markanswered (Boolean) — when a message is replied to and this variable is set, it is marked as having been answered. See the section "Message states". 👑
mbox-fcc-and-pcc (Boolean) — by default all file and pipe message receivers (see expandaddr) will be fed valid MBOX database entry message data (see folder, mbox-rfc4155), and existing file targets will become extended in compliance to RFC 4155. If this variable is unset then a plain standalone RFC 5322 message will be written, and existing file targets will be overwritten. 😭 so yeah, know which mode you're in.
mbox-rfc4155 (Boolean) — when opening MBOX mailbox databases, and in order to achieve compatibility with old software, the very tolerant POSIX standard rules for detecting message boundaries (so-called From_ lines) are used instead of the stricter rules from the standard RFC 4155. This behaviour can be switched by setting this variable.

This may temporarily be handy when S-nail complains about invalid From_ lines when opening a MBOX: in this case setting this variable and re-opening the mailbox in question may correct the result. If so, copying the entire mailbox to some other file, as in copy * SOME-FILE, will perform proper, all-compatible From_ quoting for all detected messages, resulting in a valid MBOX mailbox. ([v15 behaviour may differ] The better and non-destructive approach is to re-encode invalid messages, as if it would be created anew, instead of mangling the From_ lines; this requires the structural code changes of the v15 rewrite.) Finally the variable can be unset again:

define mboxfix {
  localopts yes; wysh set mbox-rfc4155;\
    wysh File "${1}"; copy * "${2}"
}
call mboxfix /tmp/bad.mbox /tmp/good.mbox

memdebug (Boolean) — internal development variable. (Keeps memory debug enabled even if debug is not set.) not for us, bestie, that's ✨dev main character energy✨
message-id-disable (Boolean) — by setting this variable the generation of Message-ID: and Content-ID: message and MIME part headers can be completely suppressed, effectively leaving this task up to the mta (Mail-Transfer-Agent) or the SMTP server. Note that according to RFC 5321 a SMTP server is not required to add this field by itself, so it should be ensured that it accepts messages without Message-ID. 💀 don't set-and-forget this one.
message-inject-head — a string to put at the beginning of each new message, followed by a newline. [Obsolete] The escape sequences tabulator \t and newline \n are understood (use the wysh prefix when setting the variable(s) instead).
message-inject-tail — a string to put at the end of each new message, followed by a newline. [Obsolete] The escape sequences tabulator \t and newline \n are understood (use the wysh prefix when setting the variable(s) instead). Also see on-compose-leave. 🎀
metoo (Boolean) — usually, when an alias expansion contains the sender, the sender is removed from the expansion. Setting this option suppresses these removals. Note that a set metoo also causes a -m option to be passed through to the mta (Mail-Transfer-Agent); though most of the modern MTAs no longer document this flag, no MTA is known which does not support it (for historical compatibility). 🌈 yes bestie we're keeping the legacy flag alive out of respect.
mime-allow-text-controls (Boolean) — when sending messages, each part of the message is MIME-inspected in order to classify the Content-Type: and Content-Transfer-Encoding: (see mime-encoding) that is required to send this part over mail transport, i.e., a computation rather similar to what the file(1) command produces when used with the --mime option.

This classification however treats text files which are encoded in UTF-16 (seen for HTML files) and similar character sets as binary octet-streams, forcefully changing any text/plain or text/html specification to application/octet-stream: if that actually happens a yet unset charset MIME parameter is set to binary, effectively making it impossible for the receiving MUA to automatically interpret the contents of the part. 😭

If this variable is set, and the data was unambiguously identified as text data at first glance (by a .txt or .html file extension), then the original Content-Type: will not be overwritten. 🫶

mime-alternative-favour-rich (Boolean) — if this variable is set then rich MIME alternative parts (e.g., HTML) will be preferred in favour of included plain text versions when displaying messages, provided that a handler exists which produces output that can be (re)integrated into S-nail's normal visual display. fancy-render mode, activated 💅
mime-counter-evidence — normally the Content-Type: field is used to decide how to handle MIME parts. Some MUAs, however, do not use "The mime.types files" (also see "HTML mail and MIME attachments") or a similar mechanism to correctly classify content, but specify an unspecific MIME type (application/octet-stream) even for plain text attachments. If this variable is set then S-nail will try to re-classify such MIME message parts, if possible, for example via a possibly existing attachment filename. A non-empty value may also be given, in which case a number is expected, actually a carrier of bits, best specified as a binary value, like 0b1111. 🧚
- If bit two is set (counting from 1, decimal 2) then the detected mimetype will be carried along with the message and be used for deciding which MIME handler is to be used, for example; when displaying such a MIME part the part-info will indicate the overridden content-type by showing a plus sign +.
- If bit three is set (decimal 4) then the counter-evidence is always produced and a positive result will be used as the MIME type, even forcefully overriding the parts given MIME type. 🔥
- If bit four is set (decimal 8) as a last resort the actual content of application/octet-stream parts will be inspected, so that data which looks like plain text can be treated as such. This mode is even more relaxed when data is to be displayed to the user or used as a message quote (data consumers which mangle data for display purposes, which includes masking of control characters, for example).
mime-encoding — the MIME Content-Transfer-Encoding to use in outgoing text messages and message parts, where applicable (7-bit clean text messages are without an encoding if possible):
8bit (or 8b) — so this one lowkey just shoves the raw data straight through unchanged, which sounds iconic until you remember that it "may cause problems when transferring mail messages over channels that are not ESMTP (RFC 1869) compliant" 😭. Also — and this is the part nobody tells you — several input data constructs are not allowed by the specifications and may cause a different transfer-encoding to be used. And by established rules and popular demand, occurrences of ^From_ (see mbox-rfc4155) will be MBOXO quoted (prefixed with greater-than sign >) instead of causing a non-destructive encoding like quoted-printable to be chosen — unless context (like message signing) requires otherwise. iykyk 💅
quoted-printable (or qp) — the chill one 🧚. It's 7-bit clean and has the property that ASCII characters are passed through unchanged, so that an english message can be read as-is; it's also acceptable for other single-byte locales that share many characters with ASCII, for example ISO-8859-1. But the overhead is giving a lot for messages in other character sets: for example it will require up to twelve (12) bytes to encode a single UTF-8 character of four (4) bytes 😬. It is the default encoding, bestie. periodt.
base64 (or b64) — the baddie 🎀. This encoding is 7-bit clean and will always be used for binary data. It's got a constant input:output ratio of 3:4 — regardless of the character set of the input data, it will encode three bytes of input to four bytes of output. This transfer-encoding is not human readable without performing a decoding step, so no peeking 🙈.

`mime-force-sendout`

(Boolean) [Option] — whenever it is not acceptable to fail sending out messages because of non-convertible character content, this variable may be set. As a last resort it will classify the part content as application/octet-stream 😤. For the complete picture of character set conversion in S-nail, go read the section "Character sets" — it's tea, honestly 🍓.

`mimetypes-load-control`

So this one controls which of "The mime.types files" get loaded, and the whole thing is basically a vibe check with letters:

If the letter u is part of the option value, then the user's personal ~/.mime.types file will be loaded (if it exists).
Likewise the letter s controls loading of the system wide /etc/mime.types.
Directives found in the user file take precedence, and letter matching is case-insensitive ✨.

If this variable is not set, S-nail will try to load both files. Incorporation of the S-nail-built-in MIME types cannot be suppressed — but they will be matched last (the order can be listed via mimetype).

More sources can be specified by using a different syntax: if the value string contains an equals sign =, then it is instead parsed as a comma-separated list of the described letters plus f=FILENAME pairs 🦋. The given filenames will be expanded and loaded, and their content may use the extended syntax that is described in the section "The mime.types files". Directives found in such files always take precedence (they're prepended to the MIME type cache) 👑.

`mta`

Pick an alternate Mail-Transfer-Agent, bestie — either by specifying the full pathname of an executable (a file:// prefix may be given), or [Option]ally a SMTP aka SUBMISSION protocol URL [v15-compat]:

submissions://[user[:password]@]server[:port]

([no v15-compat]: [smtp://]server[:port].) The default has been chosen at compile time. MTA data transfers are always performed in asynchronous child processes, and without supervision unless either the sendwait or the verbose variable is set 🫶. Also see mta-bcc-ok. [Option]ally, expansion of aliases(5) can be performed by setting mta-aliases.

For testing purposes there's the test pseudo-MTA, which dumps to standard output or optionally to a file, and honours mbox-fcc-and-pcc 💖:

$ echo text | s-nail -:/ -Smta=test -s ubject ex@am.ple
$ </dev/null s-nail -:/ -Smta=test://./xy ex@am.ple

For a file-based MTA it may be necessary to set mta-argv0 in order to choose the right target of a modern mailwrapper(8) environment. It will be passed command line arguments from several possible sources: from the variable mta-arguments if set, from the command line if given and the variable expandargv allows their use. Argument processing of the MTA will be terminated with a -- separator.

The otherwise occurring implicit usage of the following MTA command line arguments can be disabled by setting the boolean variable mta-no-default-arguments (which will also disable passing -- to the MTA):

-i — for not treating a line with only a dot . character as the end of input
-m — shall the variable metoo be set
-v — if the verbose variable is set

…and in conjunction with the -r command line option or r-option-implicit, -f as well as possibly -F will (not) be passed.

[Option]ally, S-nail can send mail over SMTP aka SUBMISSION network connections to a single defined smart host by setting this variable to a SMTP or SUBMISSION URL (see "On URL syntax and credential lookup") 🔥. An authentication scheme can be specified via the variable chain smtp-auth. Encrypted network connections are [Option]ally available — the section "Encrypted network communication" should give an overview and provide links to more information on this. Note that with some mail providers it may be necessary to set the smtp-hostname variable in order to use a specific combination of from, hostname and mta. Network communication socket timeouts are configurable via socket-connect-timeout. All generated network traffic may be proxied over a SOCKS socks-proxy, and it can be logged by setting verbose twice. The following SMTP variants may be used:

The plain SMTP protocol (RFC 5321) that normally lives on the server port 25 and requires setting the smtp-use-starttls variable to enter a TLS encrypted session state. Assign a value like [v15-compat] smtp://[user[:password]@]server[:port] ([no v15-compat] smtp://server[:port]) to choose this protocol.
The so-called SMTPS which is supposed to live on server port 465 and is automatically TLS secured. Unfortunately it never became a standardized protocol and may thus not be supported by your hosts network service database — in fact the port number has already been reassigned to other protocols 💀!

SMTPS is nonetheless a commonly offered protocol and thus can be chosen by assigning a value like [v15-compat] smtps://[user[:password]@]server[:port] ([no v15-compat] smtps://server[:port]); due to the mentioned problems it is usually necessary to explicitly specify the port as :465, however.

The SUBMISSION protocol (RFC 6409) lives on server port 587 and is identically to the SMTP protocol from S-nail's point of view; it requires setting smtp-use-starttls to enter a TLS secured session state; e.g., [v15-compat] submission://[user[:password]@]server[:port].
The SUBMISSIONS protocol (RFC 8314) that lives on server port 465 and is TLS secured by default. It can be chosen by assigning a value like [v15-compat] submissions://[user[:password]@]server[:port]. Due to the problems mentioned for SMTPS above and the fact that SUBMISSIONS is new and a successor that lives on the same port as the historical engineering mismanagement named SMTPS, it is usually necessary to explicitly specify the port as :465 😭.

`mta-aliases`

[Option] — if set to a path pointing to a text file in valid MTA (Postfix) aliases(5) format, the file is loaded and cached (manageable with mtaaliases), and henceforth plain name (see expandaddr) message receiver names are recursively expanded as a last expansion step, after the distribution lists which can be created with alias ✨. Constraints on aliases(5) content support, ngl this is specific:

only local addresses (names) which are valid usernames ([a-z_][a-z0-9_-]*[$]?) are treated as expandable aliases
and [v15 behaviour may differ] :include:/file/name directives are not supported 🙅

By including -name in expandaddr it can be asserted that only expanded names (mail addresses) are passed through to the MTA.

`mta-arguments`

Arguments to pass through to a file-based mta (Mail-Transfer-Agent), parsed according to "Shell-style argument quoting" into an array of arguments which will be joined onto MTA options from other sources, for example:

? wysh set mta-arguments='-t -X "/tmp/my log"'

slay 🎀

`mta-no-default-arguments`

(Boolean) Avoids passing standard command line options to a file-based mta (please see there 👀).

`mta-no-receiver-arguments`

(Boolean) By default all receiver addresses will be passed as command line options to a file-based mta. Setting this variable disables this behaviour to aid those MTAs which employ special treatment of such arguments. Doing so can make it necessary to pass a -t via mta-arguments, to testify the MTA that it should use the passed message as a template 🫡.

`mta-argv0`

okay so bestie, this one is all about the mailwrapper(8) situation 👀 lots of systems use a so-called mailwrapper(8) environment to stay compatible with sendmail(1), and the way that works is that it peeks at the name that was used to invoke the mail delivery system. so if this variable is set, the mailwrapper (aka the program that actually gets executed when you call the file-based mta) will treat its contents as that name. that's the whole vibe. ✨

`mta-bcc-ok`

(Boolean) so this is a little spicy 🌶️ — in violation of RFC 5322, some MTAs just do not remove Bcc: header lines from transported messages after they've noted the respective receivers for addressing purposes. (The MTAs Exim and Courier, for example, require the command line option -t to enforce removal.) Unless this is set, corresponding receivers are addressed by protocol-specific means or MTA command line options only, and the header itself is stripped before being sent over the wire. iconic behaviour tbh 💅

`netrc-lookup-USER@HOST`, `netrc-lookup-HOST`, `netrc-lookup`

(Boolean) [v15-compat] [Option] — used to control usage of the user's ~/.netrc file for lookup of account credentials, as documented in the section “On URL syntax and credential lookup” and for the command netrc; the section “The .netrc file” documents the file format. also see netrc-pipe. 🎀

`netrc-pipe`

[v15-compat] [Option] — when ~/.netrc is loaded (see netrc and netrc-lookup) then S-nail will read the output of a shell pipe instead of the user's ~/.netrc file if this variable is set (to the desired shell command). this is genuinely such a slay feature because it can be used to, for example, store ~/.netrc in encrypted form:

? set netrc-pipe='gpg -qd ~/.netrc.pgp'

encrypted creds era 🔐✨

`newfolders`

[Option] — if this variable has the value maildir, newly created local folders will be in Maildir instead of MBOX format. simple as that, no cap 🦋

`newmail`

checks for new mail in the current folder each time the prompt is shown. a Maildir folder must be re-scanned to determine if new mail has arrived. if this variable is set to the special value nopoll then a Maildir folder will not be rescanned completely, but only timestamp changes are detected. Maildir folders are [Option]al. 📬

`outfolder`

(Boolean) — causes a non-absolute filename specified in record, as well as the sender-based filenames of the Copy, Save, Followup and followup commands, to be interpreted relative to the folder directory rather than relative to the current directory. path logic: handled 💅

`on-account-cleanup-ACCOUNT`, `on-account-cleanup`

macro hook which will be called once an account is left, as the very last step before unrolling per-account localopts. this hook is run even in case of fatal errors, including those generated by switching to the account as such 😭 so it is advisable to perform only absolutely necessary actions, like cleaning up alternates, for example. the specialized form is used in favour of the generic one if found. 🫶

`on-compose-cleanup`

macro hook which will be called after the message has been sent (or not, in case of failures), as the very last step before unrolling compose mode localopts. this hook is run even in case of fatal errors, and it is advisable to perform only absolutely necessary actions, like cleaning up alternates, for example. 💀

for compose mode hooks that may affect the message content please see on-compose-enter, on-compose-leave, on-compose-splice. [v15 behaviour may differ] this hook exists because alias, alternates, commandalias, shortcut, to name a few, are neither covered by localopts nor by local: changes applied in compose mode will continue to be in effect thereafter. so like… forever. 🙈

`on-compose-enter`, `on-compose-leave`

macro hooks which will be called once compose mode is entered, and after composing has been finished, respectively; the exact order of the steps taken is documented for ~., one of the “COMMAND ESCAPES”. context about the message being worked on can be queried via digmsg. localopts are enabled for these hooks, and changes on variables will be forgotten after the message has been sent. on-compose-cleanup can be used to perform other necessary cleanup steps. ✨

here is an example that injects a signature via message-inject-tail; instead using on-compose-splice to simply inject the file of desire via ~< or ~<! may be a better approach.

define t_ocl {
  vput ! i cat ~/.mysig
  if $? -eq 0
     vput csop message-inject-tail trim-end $i
  end

  # Alternatively
  readctl create ~/.mysig
  if $? -eq 0
    readall i
    if $? -eq 0
      vput csop message-inject-tail trim-end $i
    end
    readctl remove ~/.mysig
  end
}
set on-compose-leave=t_ocl

`on-compose-splice`, `on-compose-splice-shell`

these hooks run once the normal compose mode is finished, but before the on-compose-leave macro hook is called etc. both hooks will be executed in a subprocess, with their input and output connected to S-nail such that they can act as if they would be an interactive user. the difference in between them is that the latter is a SHELL command, whereas the former is a normal defined macro, but which is restricted to a small set of commands (the verbose output of for example list will indicate said capability). localopts are enabled for these hooks (in the parent process), causing any setting to be forgotten after the message has been sent; on-compose-cleanup can be used to perform other cleanup as necessary. 🌸

during execution of these hooks S-nail will temporarily forget whether it has been started in interactive mode, (a restricted set of) “COMMAND ESCAPES” will always be available, and for guaranteed reproducibilities sake escape and ifs will be set to their defaults. the compose mode command ~^ has been especially designed for scriptability (via these hooks). the first line the hook will read on its standard input is the protocol version of said command escape, currently 0 0 2: backward incompatible protocol changes have to be expected. 👀

care must be taken to avoid deadlocks and other false control flow: if both involved processes wait for more input to happen at the same time, or one does not expect more input but the other is stuck waiting for consumption of its output, etc. there is no automatic synchronization of the hook: it will not be stopped automatically just because it, e.g., emits ~x. the hooks will however receive a termination signal if the parent enters an error condition. [v15 behaviour may differ] protection against and interaction with signals is not yet given; it is likely that in the future these scripts will be placed in an isolated session, which is signalled in its entirety as necessary. 😭

define ocs_signature {
  read version
  echo '~< ~/.mysig' # '~<! fortune pathtofortunefile'
}
set on-compose-splice=ocs_signature

wysh set on-compose-splice-shell=$'\
  read version;\
  printf "hello $version!  Headers: ";\
  echo \'~^header list\';\
  read status result;\
  echo "status=$status result=$result";\
  '

define ocsm {
  read version
  echo Splice protocol version is $version
  echo '~^h l'; read hl; vput csop es subs "${hl}" 0 1
  if "$es" != 2
    echoerr 'Cannot read header list'; echo '~x'; xit
  endif
  if "$hl" !%?case ' cc'
    echo '~^h i cc "Diet is your <mirr.or>"'; read es;\
      vput csop es substring "${es}" 0 1
    if "$es" != 2
      echoerr 'Cannot insert Cc: header'; echo '~x'
      # (no xit, macro finishes anyway)
    endif
  endif
}
set on-compose-splice=ocsm

`on-history-addition`

this hook will be called if an entry is about to be added to the history of the MLE, as documented in “On terminal control and line editor”. it will be called with three arguments: the first is the name of the input context (see bind), the second is either an empty string or the matching history-gabby type, and the third being the complete command line to be added. the entry will not be added to history if the hook uses a non-0 return. 💅 [v15 behaviour may differ] a future version will give the expanded command name as the third argument, followed by the tokenized command line as parsed in the remaining arguments, the first of which is the original unexpanded command name; i.e., one may do shift 4 and will then be able to access the positional parameters as usual via *, #, 1 etc. 🧚

`on-main-loop-tick`

this hook will be called whenever the program's main event loop is about to read the next input line. note variable and other changes it performs are not scoped as via localopts! ⭐

`on-program-exit`

this hook will be called when the program exits, whether via exit or quit, or because the send mode is done. note: this runs late and so terminal settings etc. are already teared down. 💀 goodbye era

`on-resend-cleanup`

[v15 behaviour may differ] identical to on-compose-cleanup, but is only triggered by resend. short and sweet 🍓

on-resend-enter — [v15 behaviour may differ] literally the same thing as on-compose-enter, except it only fires on resend; rn there's no digmsg support for it, for example. 😭
page — (Boolean) if you set this, every message that gets fed through the command you gave for pipe gets followed by a formfeed character ‘\f’. cute little page break, slay. 📄
password-USER@HOST, password-HOST, password — [v15-compat] this is the variable chain that sets a password, and it's used when no password has been given in the protocol and the account-specific URL; as a last resort S-nail will ask you for a password on your terminal if the auth method actually needs one. > ⚠️ bestie listen — specifying passwords in a startup file is generally a security risk, so the file should be readable by the invoking user ONLY. no sharing, periodt. 🔐
password-USER@HOST — [no v15-compat] (peep the chain above if you're on [v15-compat]) this sets the password for ‘USER’ when connecting to ‘HOST’. If there's no such variable defined for a host, the user gets asked for a password on standard input. Same energy as above: > ⚠️ passwords in a startup file are generally a security risk; that file should be readable by the invoking user only. 🙈
piperaw — (Boolean) sends messages to the pipe command without doing the MIME and character set conversions. raw vibes only. 🧚
pipe-TYPE/SUBTYPE — when a MIME message part of type ‘TYPE/SUBTYPE’ (case-insensitive, bestie) is displayed or quoted, its text gets filtered through the value of this variable, which S-nail interprets as a shell command. Note that only parts which can be displayed inline as plain text (see copiousoutput) are displayed unless otherwise noted — other MIME parts will only be considered by and for the mimeview command. 👑

The special value question mark ‘?’ forces interpretation of the message part as plain text, so for example set pipe-application/xml=? will henceforth display XML "as is". (You could also achieve the same thing by adding a MIME type marker with the mimetype command. And [Option]ally MIME type handlers may be defined via "The Mailcap files" — these directives, copiousoutput has already been used, should be referred to for further documentation.)

The question mark ‘?’ can in fact be used as a trigger character to adjust usage and behaviour of a following shell command specification more thoroughly, by appending more special characters which refer to further mailcap directives. For example, this hypothetical command specification could be used:

? set pipe-X/Y='?!++=? vim ${MAILX_FILENAME_TEMPORARY}'

‘*’ — the command produces plain text to be integrated in S-nail's output: copiousoutput.
‘#’ — if set, the handler will NOT be invoked when a message is to be quoted, but only when it will be displayed: x-mailx-noquote.
‘&’ — run the command asynchronously, i.e., without blocking S-nail: x-mailx-async. The standard output of the command will go to /dev/null.
‘!’ — the command must be run on an interactive terminal, so S-nail will temporarily release the terminal to it: needsterminal.
‘+’ — request creation of a zero-sized temporary file, the absolute pathname of which will be made accessible via the environment variable MAILX_FILENAME_TEMPORARY: x-mailx-tmpfile. If given twice then the file will be unlinked automatically by S-nail when the command loop is entered again at latest: x-mailx-tmpfile-unlink; and it is an error to use automatic deletion in conjunction with x-mailx-async. 💀
‘=’ — normally the MIME part content is passed to the handler via standard input; if this flag is set then the data will instead be written into MAILX_FILENAME_TEMPORARY (x-mailx-tmpfile-fill), the creation of which is implied; in order to cause automatic deletion of the temporary file, two plus signs ‘++’ still have to be used.
‘?’ — to avoid ambiguities with normal shell command content, another question mark can be used to forcefully terminate interpretation of remaining characters. (Any character not in this list will have the same effect.)

Some information about the MIME part to be displayed is embedded into the environment of the shell command:

MAILX_CONTENT — the MIME content-type of the part, if known, the empty string otherwise.
MAILX_CONTENT_EVIDENCE — if mime-counter-evidence includes the carry-around-bit (2), then this will be set to the detected MIME content-type; not only then identical to MAILX_CONTENT otherwise.
MAILX_EXTERNAL_BODY_URL — MIME parts of type ‘message/external-body access-type=url’ will store the access URL in this variable, it is empty otherwise. > ⚠️ URL targets should not be activated automatically, without supervision. fr fr, don't just let random URLs run themselves. 🙅‍♀️
MAILX_FILENAME — the filename, if any is set, the empty string otherwise.
MAILX_FILENAME_GENERATED — a random string. ✨
MAILX_FILENAME_TEMPORARY — if temporary file creation has been requested through the command prefix, this variable will be set and contain the absolute pathname of the temporary file.

pipe-EXTENSION — identical to pipe-TYPE/SUBTYPE except that ‘EXTENSION’ (normalized to lowercase using character mappings of the ASCII charset) names a file extension, for example ‘xhtml’. Handlers registered using this method take precedence. 👑
pop3-auth-USER@HOST, pop3-auth-HOST, pop3-auth — [Option][v15-compat] variable chain that sets the POP3 authentication method. Supported are the default ‘plain’, [v15-compat] ‘oauthbearer’ (see the "FAQ" entry "But, how about XOAUTH2 / OAUTHBEARER?"), as well as [v15-compat] ‘external’ and ‘externanon’ for TLS secured connections which pass a client certificate via tls-config-pairs. There may be the [Option]al method [v15-compat] ‘gssapi’. ‘externanon’ does not need any user credentials, ‘external’ and ‘gssapi’ need a user, and the remains also require a password. ‘externanon’ solely builds upon the credentials passed via a client certificate, and is usually the way to go since tested servers do not actually follow RFC 4422 and fail if additional credentials are actually passed. Unless pop3-no-apop is set, the ‘plain’ method will [Option]ally be replaced with APOP if possible (see there). 💅
pop3-bulk-load-USER@HOST, pop3-bulk-load-HOST, pop3-bulk-load — (Boolean)[Option] when accessing a POP3 server S-nail loads the headers of the messages, and only requests the message bodies on user request. For the POP3 protocol this means the message headers will be downloaded twice. If this variable is set then S-nail will download only complete messages from the given POP3 server(s) instead. no more double-dipping 🍓
pop3-keepalive-USER@HOST, pop3-keepalive-HOST, pop3-keepalive — [Option] POP3 servers close the connection after a period of inactivity; the standard requires this to be at least 10 minutes, but practical experience may vary, ngl. Setting this variable to a numeric value greater than ‘0’ causes a ‘NOOP’ command to be sent each value seconds if no other operation is performed. keep that connection fed 🫶
pop3-no-apop-USER@HOST, pop3-no-apop-HOST, pop3-no-apop — (Boolean)[Option] unless this variable is set, the MD5 based ‘APOP’ authentication method will be used instead of a chosen ‘plain’ pop3-auth when connecting to a POP3 server that advertises support. The advantage of ‘APOP’ is that only a single packet is sent for the user/password tuple. (Originally also that the password is not sent in clear text over the wire, but for one, MD5 does not any longer offer sufficient security, and then today transport is almost ever TLS secured.) Note that pop3-no-apop-HOST requires [v15-compat]. 😬
pop3-use-starttls-USER@HOST, pop3-use-starttls-HOST, pop3-use-starttls — (Boolean)[Option] causes S-nail to issue a ‘STLS’ command to make an unencrypted POP3 session TLS encrypted. This functionality is not supported by all servers, and is not used if the session is already encrypted by the POP3S method. Note that pop3-use-starttls-HOST requires [v15-compat]. 🔒✨
posix — (Boolean) this flag enables POSIX mode, which changes behaviour of S-nail where that deviates from standardized behaviour. It is automatically squared with the environment variable POSIXLY_CORRECT — changing the one will adjust the other. The following behaviour is covered and enforced by this mechanism:
🫶 In non-interactive mode, any error that pops up while loading resource files during program startup will cause a program exit, whereas in interactive mode those errors just stop the loading of the currently loaded (stack of) file(s), i.e. recursively. You can dodge these exits on a per-command basis with ignerr, one of the “Command modifiers”, for each command that's allowed to fail. 💅
alternates will replace the list of alternate addresses instead of appending to it. Also, alternates only get honoured for any sort of message reply, and for aliases. no cap
The variables that insert “COMMAND ESCAPES” ~A, ~a, ~I and ~i will expand embedded character sequences '\t' horizontal tabulator and '\n' line feed. [v15 behaviour may differ] For compatibility reasons this step will always be performed. ⭐
Reading in messages via ~f (“COMMAND ESCAPES”) will use the type not the forward headerpick selection.
Upon changing the active folder, no summary of headers will be displayed even if header is set. 😭
Setting ignoreeof implies the behaviour described by dot.
The variable keep is extended to cover any empty mailbox, not only empty “primary system mailbox”es: they will be removed when they're otherwise left in empty state. 🧚

`print-alternatives`

(Boolean) When a MIME message part of type multipart/alternative is displayed and it contains a subpart of type text/plain, the other parts are normally discarded. Setting this variable causes all subparts to be displayed, just as if the surrounding part was of type multipart/mixed. it's giving completionist 💖

`prompt`

The string used as a prompt in interactive mode. Whenever the variable is evaluated, the value is treated as if specified within dollar-single-quotes (see “Shell-style argument quoting”). This (post-assignment, i.e. second) expansion can be used to embed status information — for example ?, !, account or mailbox-display. 🔥

In order to embed characters that should not be counted when calculating the visual width of the resulting string, enclose the characters of interest in a pair of reverse solidus escaped brackets: \[\E[0m\]; a slot for coloured prompts is also available with the [Option]al command colour. Prompting may be prevented by setting this to the null string (aka set noprompt). 🎀

`prompt2`

This string is used for secondary prompts, but is otherwise identical to prompt. The default is .. . 🦋

`quiet`

(Boolean) Suppresses the printing of the version when first invoked. lowkey the introvert setting 🙈

`quote`

If set, messages processed by variants of followup and reply will start with the original message, lines of which are prefixed by indentprefix, taking into account quote-chars and quote-fold. No headers will be quoted when set without value or for noheading, for headers the type headerpick selection will be included in the quote, allbodies embeds the (body) contents of all MIME parts, and allheaders also includes all headers. The quoted message will be enclosed by the expansions of quote-inject-head and quote-inject-tail. Also see quote-add-cc, quote-as-attachment and ~Q, one of the “COMMAND ESCAPES”. 💌

`quote-add-cc`

(Boolean) Whether senders of messages quoted via ~Q shall be made members of the carbon copies Cc: list.

`quote-as-attachment`

(Boolean) Add the original message in its entirety as a message/rfc822 MIME attachment when replying to a message. Note this works regardless of the setting of quote. 😭 iconic and independent

`quote-chars`

Can be set to a string consisting of non-whitespace ASCII characters which shall be treated as quotation leaders, the default being >|}:. 🍓

`quote-fold`

[Option] Can be set in addition to indentprefix, and creates a more fancy quotation in that leading quotation characters (quote-chars) are compressed and overlong lines are folded. quote-fold can be set to either one, two or three (space separated) numeric values, which are interpreted as the maximum (goal) and the minimum line length, respectively, in a spirit rather equal to the fmt(1) program, but line- instead of paragraph-based. The third value is used as the maximum line length instead of the first if no better break point can be found; it is ignored unless it's larger than the minimum and smaller than the maximum. If not set explicitly the minimum will reflect the goal algorithmically. The goal cannot be smaller than the length of indentprefix plus some additional pad; necessary adjustments take place silently. ✨

`quote-inject-head`, `quote-inject-tail`

The strings to put before and after the text of a quoted message, if non-empty, and respectively. The former defaults to %f wrote:\n\n. Special format directives will be expanded if possible, and if so configured the output will be folded according to quote-fold. Format specifiers in the given strings start with a percent sign % and expand values of the original message, unless noted otherwise. Note that names and addresses are not subject to the setting of showto. Valid format specifiers are: 💅

%% — a plain percent sign.
%a — the address(es) of the sender(s).
%d — the date found in the Date: header of the message when datefield is set (the default), otherwise the date when the message was received. Formatting can be controlled by assigning a strftime(3) format string to datefield (and datefield-markout-older).
%f — the full name(s) (name and address, as given) of the sender(s).
%i — the Message-ID:.
%n — the real name(s) of the sender(s) if there is one and showname allows usage, the address(es) otherwise.
%r — the senders real name(s) if there is one, the address(es) otherwise.

`r-option-implicit`

(Boolean) Setting this option evaluates the contents of from (or, if that contains multiple addresses, sender) and passes the results onto the used (file-based) MTA as described for the -r option (empty argument case). 🫶

`recipients-in-cc`

(Boolean) When doing a reply, the original From: and To: as well as addressees which possibly came in via Reply-To: and Mail-Followup-To: are by default merged into the new To:. If this variable is set, a sensitive algorithm tries to place in To: only the sender of the message being replied to, and the others are placed in Cc:. the way it socialises your headers 😌

`record`

Unless this variable is defined, no copies of outgoing mail will be saved. If defined it gives the pathname, subject to the usual “Filename transformations”, of a folder where all new, replied-to or forwarded messages are saved: when saving to this folder fails the message is not sent, but instead saved to DEAD. 💀 The standard defines that relative (fully expanded) paths are to be interpreted relative to the current directory (cwd); to force interpretation relative to folder, outfolder needs to be set in addition.

`record-files`

(Boolean) If this variable is set, the meaning of record will be extended to cover messages which target only file and pipe recipients (see expandaddr). These address types will not appear in recipient lists unless add-file-recipients is also set.

`record-resent`

(Boolean) If this variable is set, the meaning of record will be extended to also cover the resend and Resend commands.

`reply-in-same-charset`

(Boolean) If this variable is set, S-nail first tries to use the same character set of the original message for replies. If this fails, the mechanism described in “Character sets” is evaluated as usual. 🌈

`reply-strings`

Can be set to a comma-separated list of (case-insensitive according to ASCII rules) strings which shall be recognized in addition to the built-in strings as Subject: reply message indicators — built-in are Re:, which is mandated by RFC 5322, as well as the german Aw:, Antw:, and the Wg: which often has been seen in the wild; I.e., the separating colon has to be specified explicitly. 👑

`reply-to`

A list of addresses to put into the Reply-To: field of the message header. Members of this list are handled as if they were in the alternates list.

`replyto`

[Obsolete] Variant of reply-to. ngl she's a legacy icon 💀

`reply-to-honour`

Controls whether a Reply-To: header is honoured when replying to a message via reply or Lreply. This is a “quadoption”; if set without a value it defaults to “yes”.

`reply-to-swap-in`

Standards like DKIM and (in conjunction with) DMARC caused many “Mailing lists” to use sender address rewriting in the style of Name via List <list@address>, where the original sender address often being placed in Reply-To:. If this is set and a Reply-To: exists, and consists of only one addressee (!), then that is used in place of the pretended sender. This works independently from reply-to-honour. The optional value, a comma-separated list of strings, offers more fine-grained control on when swapping shall be used; for now supported is mlist, here swapping occurs if the sender is a mailing-list as defined by mlist. 🔥 the way she sees through the masquerade fr fr

rfc822-body-from_ — (Boolean) okay so sometimes a whole email gets stuffed inside another email via the message/rfc822 MIME mechanism, right? And this little icon here forces S-nail to show you a so-called ‘From_’ line for those embedded messages, purely for ✨visual convenience✨. Also peep mbox-rfc4155 while you're at it 👀
save — (Boolean) turns on saving of (partial) messages into DEAD if you get interrupted or a delivery error happens. Your half-baked lil messages get a lil graveyard 🪦💀
screen — the number of lines that counts as a “screenful” of lines. Where's it used? In the headers summary display, from searching, in message topline display, and when scrolling with z. Bestie if you don't set this, S-nail just vibes and calculates it from the detected terminal window size plus the baud rate: the faster the terminal, the more it shows 🏎️✨ Overall screen dimensions and pager usage are influenced by the environment variables COLUMNS and LINES and the variable crt 🫶
searchheaders — (Boolean) expands message list specifiers shaped like /x:y into all messages that contain the substring “y” in the header field x. And the string search is case insensitive, so no need to yell 🔍💅
sendcharsets — [Option] a comma-separated list of character set names that can be used in outgoing internet mail 📮 The value of the variable charset-8bit is automatically appended to this list of character sets, no cap. If no character set conversion capabilities are compiled into S-nail, then the only supported charset is ttycharset. Also see sendcharsets-else-ttycharset and go read the section “Character sets” for the complete picture of character set conversion in S-nail 🌈
sendcharsets-else-ttycharset — (Boolean)[Option] so if this variable is set, but sendcharsets is not, then S-nail acts like sendcharsets had been set to the value of the variable ttycharset. In effect this combo passes the message data straight through in the character set of the current locale encoding 🌀 so mail message text will be (assumed to be) in ISO-8859-1 encoding when sent from within an ISO-8859-1 locale, and in UTF-8 encoding when sent from within a UTF-8 locale.

The 8-bit fallback charset-8bit never comes into play here, because ttycharset is implicitly assumed to be 8-bit and capable to represent all files the user may specify (as is the case when no character set conversion support is available in S-nail and the only supported character set is ttycharset, see “Character sets”). This might be a problem for scripts which use the suggested LC_ALL=C setting, since in this case the character set is US-ASCII by definition 😭 so it's better to also override ttycharset, then; and/or do something like the following in the resource file:

# Avoid ASCII "propagates to 8-bit" when scripting
\if ! t && "$LC_ALL" != C && "$LC_CTYPE" != C
  \set sendcharsets-else-ttycharset
\end

sender — an address that gets put into the ‘Sender:’ field of outgoing messages 📨 quoting RFC 5322: the mailbox of the agent responsible for the actual transmission of the message. This field should normally not be used unless the from field contains more than one address, in which case it is required. [v15 behaviour may differ] Please expect automatic management of the from and sender relationship 🤝 Dependent on the context this address is handled as if it were in the list of alternates. Also see -r, r-option-implicit.
sendmail — [Obsolete] the predecessor of mta. That's it, that's the whole thing, she's retired 👵
sendmail-arguments — [Obsolete] predecessor of mta-arguments.
sendmail-no-default-arguments — [Obsolete](Boolean) predecessor of mta-no-default-arguments.
sendmail-progname — [Obsolete] predecessor of mta-argv0.
sendwait — so sending messages to the chosen mta or to command-pipe receivers (see “On sending mail, and non-interactive mode”) will be performed asynchronously ⏳ which means only startup errors of the respective program will be recognizable, but no delivery errors 😬 Also, no guarantees can be made as to when the respective program will actually run, as well as to when they will have produced output.

If this variable is set then child program exit is waited for, and its exit status code is used to decide about success ✅ Remarks: in conflict with the POSIX standard this variable is built-in to be initially set 🫢 Another difference is that it can have a value, which is interpreted as a comma-separated list of case-insensitive strings naming specific subsystems for which synchronousness shall be ensured (only). Possible values are ‘mta’ for mta delivery, and ‘pcc’ for command-pipe receivers.

showlast — (Boolean) this setting causes S-nail to start at the last message instead of the first one when opening a mail folder, as well as with from and headers 🔚✨
showname — (Boolean) causes S-nail to use the sender's real name instead of the plain address in the header field summary and in message specifications 🪪
showto — (Boolean) causes the recipient of the message to be shown in the header summary if the message was sent by the user 👀
Sign — the value backing ~A, one of the “COMMAND ESCAPES” 💌 Also see message-inject-tail, on-compose-leave and on-compose-splice.
sign — the value backing ~a, one of the “COMMAND ESCAPES” ✍️ Also see message-inject-tail, on-compose-leave and on-compose-splice.
signature — [Obsolete] bestie please use on-compose-splice or on-compose-splice-shell or on-compose-leave and (if necessary) message-inject-tail instead! 🙏
skipemptybody — (Boolean) if an outgoing message has an empty first or only message part, do not send, but discard it, successfully 🗑️✨ (also see the command line option -E).
smime-ca-dir, smime-ca-file — [Option] specify the location of trusted CA certificates in PEM (Privacy Enhanced Mail) for the purpose of verification of S/MIME signed messages 🔐 tls-ca-dir documents the necessary preparation steps to use the former. The set of CA certificates which are built into the TLS library can be explicitly turned off by setting smime-ca-no-defaults, and further fine-tuning is possible via smime-ca-flags.
smime-ca-flags — [Option] can be used to fine-tune behaviour of the X509 CA certificate storage, and the certificate verification that is used. The actual values and their meanings are documented for tls-ca-flags ⚙️
smime-ca-no-defaults — (Boolean)[Option] do not load the default CA locations that are built into the used to TLS library to verify S/MIME signed messages 🚫
smime-cipher-USER@HOST, smime-cipher — [Option] specifies the cipher to use when generating S/MIME encrypted messages (for the specified account) 🔒 RFC 5751 mandates a default of ‘aes128’ (AES-128 CBC). Possible values are (case-insensitive and) in decreasing cipher strength: ‘aes256’ (AES-256 CBC), ‘aes192’ (AES-192 CBC), ‘aes128’ (AES-128 CBC), ‘des3’ (DES EDE3 CBC, 168 bits; default if ‘aes128’ is not available) and ‘des’ (DES CBC, 56 bits).

The actually available cipher algorithms depend on the cryptographic library that S-nail uses. [Option] Support for more cipher algorithms may be available through dynamic loading via EVP_get_cipherbyname(3) (OpenSSL) if S-nail has been compiled to support this 🧚

smime-crl-dir — [Option] specifies a directory that contains files with CRLs in PEM format to use when verifying S/MIME messages 📂
smime-crl-file — [Option] specifies a file that contains a CRL in PEM format to use when verifying S/MIME messages 📄
smime-encrypt-USER@HOST — [Option] if this variable is set, messages sent to the given receiver are encrypted before sending 🔐 The value of the variable must be set to the name of a file that contains a certificate in PEM format.

If a message is sent to multiple recipients, each of them for whom a corresponding variable is set will receive an individually encrypted message; other recipients will continue to receive the message in plain text unless the smime-force-encryption variable is set 😳 It is recommended to sign encrypted messages, i.e., to also set the smime-sign variable. content-description-smime-message will be inspected for messages which become encrypted 👑

smime-force-encryption — (Boolean)[Option] causes S-nail to refuse sending unencrypted messages 🛑 no plaintext on her watch, periodt
smime-sign — (Boolean)[Option] S/MIME sign outgoing messages with the user's (from) private key and include the users certificate as a MIME attachment ✍️ Signing a message enables a recipient to verify that the sender used a valid certificate, that the email addresses in the certificate match those in the message header and that the message content has not been altered. It does not change the message text, and people will be able to read the message as usual 🫶 content-description-smime-signature will be inspected. Also see smime-sign-cert, smime-sign-include-certs and smime-sign-digest.
smime-sign-cert-USER@HOST, smime-sign-cert — [Option] points to a file in PEM format 📜 For the purpose of signing and decryption this file needs to contain the user's private key, followed by his certificate.

Okay so for message signing, ‘USER@HOST’ is always derived from the value of from — or, if that whole thing contains multiple addresses, then from sender instead. For encryption purposes, what's expected is the recipient's public encryption key (their certificate), and the certsave command is your girl for saving certificates of signed messages (peep the section “Signed and encrypted messages with S/MIME” for the deets). This whole mode of operation is usually driven by the specialized form. 💅

When you're decrypting messages, the account gets derived from the recipient fields (‘To:’ and ‘Cc:’) of the message — those get searched for addresses that have such a variable set. S-nail always uses the first address that matches, so bestie, if the same message got sent to more than one of your addresses using different encryption keys, decryption might just fail. 😭 Not a vibe, but that's the rule.

Password-encrypted keys may be used for signing and decryption. Automated password lookup is possible via the “pseudo-hosts” ‘USER@HOST.smime-cert-key’ for the private key, and ‘USER@HOST.smime-cert-cert’ for the certificate stored in the same file. For example, the hypothetical address ‘bob@exam.ple’ could be driven with a private key / certificate pair path defined in smime-sign-cert-bob@exam.ple, and the needed passwords would then be looked up as ‘bob@exam.ple.smime-cert-key’ and ‘bob@exam.ple.smime-cert-cert’. When decrypting, the value of from will be tried as a fallback to provide the necessary ‘USER@HOST’. To include intermediate certificates, use smime-sign-include-certs. The possible password sources are documented in “On URL syntax and credential lookup”. 🎀

smime-sign-digest-USER@HOST, smime-sign-digest — [Option] Specifies the message digest to use when signing S/MIME messages. Please remember that for this use case ‘USER@HOST’ refers to the variable from (or, if that contains multiple addresses, sender). The available algorithms depend on the used cryptographic library, but at least one usable built-in algorithm is ensured as a default. If possible the standard RFC 5751 will be violated by using ‘SHA512’ instead of the mandated ‘SHA1’ due to security concerns. This variable is ignored for very old (released before 2010) cryptographic libraries which do not offer the necessary interface: it will be logged if that happened. 👑

S-nail will try to add built-in support for the following message digests, names are case-insensitive: ‘BLAKE2b512’, ‘BLAKE2s256’, ‘SHA3-512’, ‘SHA3-384’, ‘SHA3-256’, ‘SHA3-224’, as well as the widely available ‘SHA512’, ‘SHA384’, ‘SHA256’, ‘SHA224’, and the proposed insecure ‘SHA1’, finally ‘MD5’. More digests may [Option]ally be available through dynamic loading via the OpenSSL function EVP_get_digestbyname(3).

smime-sign-include-certs-USER@HOST, smime-sign-include-certs — [Option] If used, this is supposed to consist of a comma-separated list of files, each of which containing a single certificate in PEM format to be included in the S/MIME message in addition to the smime-sign-cert certificate. This can be used to include intermediate certificates of the certificate authority, in order to allow the receiver's S/MIME implementation to perform a verification of the entire certificate chain, starting from a local root certificate, over the intermediate certificates, down to the smime-sign-cert. Even though top level certificates may also be included in the chain, they will not be used for the verification on the receiver's side. 🦋

For the purpose of the mechanisms involved here, ‘USER@HOST’ refers to the content of the internal variable from (or, if that contains multiple addresses, sender). The pseudo-host ‘USER@HOST.smime-include-certs’ will be used for performing password lookups for these certificates, shall they have been given one, therefore the lookup can be automated via the mechanisms described in “On URL syntax and credential lookup”.

smime-sign-message-digest-USER@HOST, smime-sign-message-digest — [Obsolete][Option] Predecessor(s) of smime-sign-digest. 💀 (like, it's giving legacy energy, respectfully)
smtp — [Obsolete][Option] To use the built-in SMTP transport, specify a SMTP URL in mta. [v15 behaviour may differ] For compatibility reasons a set smtp is used in preference of mta.
smtp-auth-USER@HOST, smtp-auth-HOST, smtp-auth — [Option] Variable chain that controls the SMTP mta authentication method. Possible values are ‘none’ ([no v15-compat] default), ‘plain’ ([v15-compat] default), ‘login’, [v15-compat] ‘oauthbearer’ (see “FAQ” entry “But, how about XOAUTH2 / OAUTHBEARER?”) as well as [v15-compat] ‘external’ and ‘externanon’ for TLS secured connections which pass a client certificate via tls-config-pairs. There may be the [Option]al methods ‘cram-md5’ and ‘gssapi’. ‘none’ and ‘externanon’ do not need any user credentials, ‘external’ and ‘gssapi’ require a user name, and all other methods require a user name and a password. ‘externanon’ solely builds upon the credentials passed via a client certificate, and is usually the way to go since tested servers do not actually follow RFC 4422 aka RFC 4954, and fail if additional credentials are passed. Also see mta. Note that smtp-auth-HOST is [v15-compat]. ([no v15-compat] Requires smtp-auth-password and smtp-auth-user. Note for smtp-auth-USER@HOST: may override dependent on sender address in the variable from.)
smtp-auth-password — [Option][no v15-compat] Sets the global fallback password for SMTP authentication. If the authentication method requires a password, but neither smtp-auth-password nor a matching smtp-auth-password-USER@HOST can be found, S-nail will ask for a password on the user's terminal. 🫶
smtp-auth-password-USER@HOST — [no v15-compat] Overrides smtp-auth-password for specific values of sender addresses, dependent upon the variable from.
smtp-auth-user — [Option][no v15-compat] Sets the global fallback user name for SMTP authentication. If the authentication method requires a user name, but neither smtp-auth-user nor a matching smtp-auth-user-USER@HOST can be found, S-nail will ask for a user name on the user's terminal. ✨
smtp-auth-user-USER@HOST — [no v15-compat] Overrides smtp-auth-user for specific values of sender addresses, dependent upon the variable from.
smtp-hostname — [Option][v15-compat] Normally S-nail uses the variable from to derive the necessary ‘USER@HOST’ information in order to issue a ‘MAIL FROM:<>’ SMTP mta command. Setting smtp-hostname can be used to use the ‘USER’ from the SMTP account (mta or the user variable chain) and the given ‘HOST’ (hostname if the empty string is given, or the local hostname as a last resort). This often allows using an address that is itself valid but hosted by a provider other than from which (in from) the message is sent. Setting this variable also influences generated ‘Message-ID:’ and ‘Content-ID:’ header fields. If the [Option]al IDNA support is available (see idna-disable) variable assignment is aborted when a necessary conversion fails. 🌸
smtp-use-starttls-USER@HOST, smtp-use-starttls-HOST, smtp-use-starttls — (Boolean)[Option] Causes S-nail to issue a ‘STARTTLS’ command to make an SMTP mta session TLS encrypted, i.e., to enable transport layer security. 🔥 (secure the bag, bestie)
socket-connect-timeout — [Option] A positive number that defines the timeout to wait for establishing a socket connection before forcing ^ERR-TIMEDOUT. ⏰
socks-proxy-USER@HOST, socks-proxy-HOST, socks-proxy — [Option] If set to the URL of a SOCKS5 server then all network activities are proxied through it, except for the single DNS name lookup necessary to resolve the proxy URL (unnecessary when given an already resolved IP address). It is automatically squared with the environment variable SOCKS5_PROXY, changing the one will adjust the other. This example creates a local SOCKS5 proxy on port 10000 that forwards to the machine ‘HOST’ (with identity ‘USER’), and from which actual network traffic happens:

$ ssh -D 10000 USER@HOST
$ s-nail -Ssocks-proxy=[socks5://]localhost:10000
# or =localhost:10000; no local DNS: =127.0.0.1:10000

spam-interface — [Option] In order to use any of the spam-related commands (like spamrate) the desired spam interface must be defined by setting this variable. Please refer to the manual section “Handling spam” for the complete picture of spam handling in S-nail. All or none of the following interfaces may be available: 🦋
spamc — the "pls talk to spamc(1)" mode, from the spamassassin(1) suite (SpamAssassin: http://spamassassin.apache.org) 💌. It is different from the generic filter interface: S-nail will automatically add the correct arguments for whatever command it's handling, and it literally has the knowledge needed to parse the program's output ✨. A default value for spamc-command will have been compiled into the S-nail binary if spamc(1) was found in PATH during compilation. If you do need to define a specific connection type (instead of using a configuration file for that), the spamc-arguments variable is your bestie, as in for example -d server.example.com -p 783. You can also specify a per-user configuration via spamc-user 🎀. Heads up: this interface does not inspect the is-spam flag of a message for the spamforget command 👀.
filter — generic spam filter support via freely configurable hooks 🪝. This interface is meant for programs like bogofilter(1), and it requires the according behaviour with respect to the hooks' exit status, at least for the spamrate command (0 meaning a message is spam, 1 for non-spam, 2 for unsure, and any other return value indicating a hard error 💀); since the hooks can include shell code snippets, diverting behaviour can be intercepted as necessary. The hooks are spamfilter-ham, spamfilter-noham, spamfilter-nospam, spamfilter-rate and spamfilter-spam; the manual section "Handling spam" contains examples for some programs 🫶. The process environment of the hooks will have the variable MAILX_FILENAME_GENERATED set. Note that spam score support for spamrate is not supported unless the [Option]tional regular expression support is available and the spamfilter-rate-scanscore variable is set.

spam-maxsize [Option] — messages that exceed this size will not be passed through to the configured spam-interface 🚫. If unset or 0, the default of 420000 bytes is used.
spamc-command [Option] — the path to the spamc(1) program for the spamc spam-interface 🛣️. Note that the path is not expanded, but used "as is" 🙈. A fallback path will have been compiled into the S-nail binary if the executable had been found during compilation.
spamc-arguments [Option] — even though S-nail deals with most arguments for the spamc spam-interface automatically, it may at least sometimes be desirable to specify connection-related ones via this variable, for example -d server.example.com -p 783 🌸.
spamc-user [Option] — specify a username for per-user configuration files for the spamc spam-interface. If this is set to the empty string, then S-nail will use the name of the current user 🫡.
spamfilter-ham, spamfilter-noham, spamfilter-nospam, spamfilter-rate, spamfilter-spam [Option] — command and argument hooks for the filter spam-interface 🪄. The manual section "Handling spam" contains examples for some programs.
spamfilter-rate-scanscore [Option] — because of the generic nature of the filter spam-interface, spam scores are not supported for it by default; but if the [Option]nal regular expression support is available, then setting this variable can be used to overcome this restriction 🌈. It is interpreted as follows: first a number (digits) is parsed that must be followed by a semicolon ; and an extended regular expression. Then the latter is used to parse the first output line of the spamfilter-rate hook, and, in case the evaluation is successful, the group that has been specified via the number is interpreted as a floating point scan score 🍓.

ssl-ca-dir-USER@HOST, ssl-ca-dir-HOST, ssl-ca-dir, ssl-ca-file-USER@HOST, ssl-ca-file-HOST, ssl-ca-file [Obsolete] [Option] — predecessors of tls-ca-file, tls-ca-dir 🦕.
ssl-ca-flags-USER@HOST, ssl-ca-flags-HOST, ssl-ca-flags [Obsolete] [Option] — predecessor of tls-ca-flags.
ssl-ca-no-defaults-USER@HOST, ssl-ca-no-defaults-HOST, ssl-ca-no-defaults [Obsolete] (Boolean) [Option] — predecessor of tls-ca-no-defaults.
ssl-cert-USER@HOST, ssl-cert-HOST, ssl-cert [Obsolete] [Option] — please use the Certificate slot of tls-config-pairs 💅.
ssl-cipher-list-USER@HOST, ssl-cipher-list-HOST, ssl-cipher-list [Obsolete] [Option] — please use the CipherString slot of tls-config-pairs.
ssl-config-file [Obsolete] [Option] — predecessor of tls-config-file.
ssl-config-module-USER@HOST, ssl-config-module-HOST, ssl-config-module [Obsolete] [Option] — predecessor of tls-config-module.
ssl-config-pairs-USER@HOST, ssl-config-pairs-HOST, ssl-config-pairs [Obsolete] [Option] — predecessor of tls-config-pairs.
ssl-crl-dir, ssl-crl-file [Obsolete] [Option] — predecessors of tls-crl-dir, tls-crl-file.
ssl-curves-USER@HOST, ssl-curves-HOST, ssl-curves [Obsolete] [Option] — please use the Curves slot of tls-config-pairs 🌀.
ssl-features [Obsolete] [Option] (Read-only) — predecessor of tls-features.
ssl-key-USER@HOST, ssl-key-HOST, ssl-key [Obsolete] [Option] — please use the PrivateKey slot of tls-config-pairs 🔑.
ssl-method-USER@HOST, ssl-method-HOST, ssl-method [Obsolete] [Option] — please use the Protocol slot of tls-config-pairs.
ssl-protocol-USER@HOST, ssl-protocol-HOST, ssl-protocol [Obsolete] [Option] — please use the Protocol slot of tls-config-pairs.
ssl-rand-file [Obsolete] [Option] — predecessor of tls-rand-file.
ssl-verify-USER@HOST, ssl-verify-HOST, ssl-verify [Obsolete] [Option] — predecessor of tls-verify.

stealthmua — if only set without an assigned value, then this setting inhibits the generation of the Message-ID:, Content-ID: and User-Agent: header fields that include obvious references to S-nail 🥷. There are two pitfalls associated with this: First, the message id of outgoing messages is not known anymore. Second, an expert may still use the remaining information in the header to track down the originating mail user agent 👀. If set to the value noagent, then the mentioned Message-ID: and Content-ID: suppression does not occur.
system-mailrc (Read-only) — the compiled in path of the system wide initialization file, one of the "Resource files": s-nail.rc 📁.
termcap ([Option]) — this specifies a comma-separated list of Terminal Information Library (libterminfo, -lterminfo) and/or Termcap Access Library (libtermcap, -ltermcap) capabilities (see "On terminal control and line editor", escape commas with reverse solidus \) to be used to overwrite or define entries 🖥️. Note this variable will only be queried once at program startup and can thus only be specified in resource files or on the command line. It will always be inspected, regardless of whether features denotes termcap/terminfo library support via ,+termcap,.

String capabilities form cap=value pairs and are expected unless noted otherwise. Numerics have to be notated as cap#number, where the number is expected in normal decimal notation. Finally, booleans do not have any value but indicate a true or false state simply by being defined or not; this indeed means that S-nail does not support undefining an existing boolean 💀. String capability values will undergo some expansions before use: for one, notations like ^LETTER stand for control-LETTER, and for clarification purposes \E can be used to specify escape (the control notation ^[ could lead to misreadings when a left bracket follows, which it does for the standard CSI sequence); finally three letter octal sequences, as in \061, are supported ✨. To specify that a terminal supports 256-colours, and to define sequences that home the cursor and produce an audible bell, one might write:

? set termcap='Co#256,home=\E[H,bel=^G'

The following terminal capabilities are or may be meaningful for the operation of the built-in line editor or S-nail in general 👑:

am (aka auto_right_margin) — a boolean that says whether the right margin needs special treatment; the xenl capability is its bestie in this whole situation, see COLUMNS for more 💫. Heads up though: this one is only used when it's backed by library support.
clear, cl (aka clear_screen) — clears the screen and homes the cursor. (It'll be simulated via ho plus cd, fyi.)
colors, Co (aka max_colors) — a numeric capability for the maximum number of colours. Ngl, S-nail doesn't actually care about the terminal beyond that, it just always emits ANSI / ISO 6429 escape sequences — also see colour ✨.
cr (aka carriage_return) — moves to the first column in the current row. The built-in fallback default is '\r' 🎀.
cub1, le (aka cursor_left) — moves the cursor left one space (non-destructively, no cap). Built-in fallback default: '\b'.
cuf1, nd (aka cursor_right) — moves the cursor right one space (also non-destructive). Built-in fallback default is '\E[C', which most terminals use. Less often you'll see '\EC' and '\EOC'.
ed, cd (aka clr_eos) — clears the screen.
el, ce (aka clr_eol) — clears to the end of the line. (Will be simulated via ch plus a whole bunch of repeated space characters 🫠.)
home, ho (aka cursor_home) — homes the cursor.
hpa, ch (aka column_address) — moves the cursor to the given column parameter, in the current row. (Will be simulated via cr plus nd.)
rmcup, te / smcup, ti (aka exit_ca_mode and enter_ca_mode, respectively) — exit and enter the alternative screen ca-mode, which effectively turns S-nail into a fullscreen application 👑. This one has to be enabled explicitly by setting termcap-ca-mode.
smkx, ks / rmkx, ke (aka keypad_xmit and keypad_local, respectively) — enable and disable the keypad. This is always enabled if it's available, because apparently even keyboards without keypads generate other key codes for stuff like cursor keys in that case, and only when it's enabled do we actually see the codes we're interested in 💅.
xenl, xn (aka eat_newline_glitch) — a boolean saying whether a newline written in the last column of an auto_right_margin-indicating terminal gets ignored. With it, the full terminal width is available even on autowrap terminals. This will be inspected even without the ,+termcap, features 👀.

Lowkey there are many more capabilities that describe key-sequences, and those are documented over at bind.

termcap-ca-mode — [Option] allows usage of the exit_ca_mode and enter_ca_mode termcapabilities so you can enter an alternative exclusive screen, the so-called ca-mode 🦋. This usually requires special configuration of the PAGER, and it also depends on the value of crt. Note: this variable will only be queried once at program startup, so it can only be specified in resource files or on the command line, bestie.
termcap-disable — [Option] disables any interaction with a terminal control library. If set, only some generic fallback built-ins and possibly the content of termcap describe the terminal to S-nail. Same deal as above: this variable is only queried once at program startup, so it can only be specified in resource files or on the command line.
tls-ca-dir-USER@HOST, tls-ca-dir-HOST, tls-ca-dir, tls-ca-file-USER@HOST, tls-ca-file-HOST, tls-ca-file — [Option] directory and file, respectively, for pools of trusted CA certificates in PEM (Privacy Enhanced Mail) format, for the purpose of verification of TLS server certificates 🔐. Concurrent use is possible: the file is loaded once needed first, and the directory lookup is performed anew as a last resort whenever necessary. The CA certificate pool built into the TLS library can be disabled via tls-ca-no-defaults, and you can fine-tune further via tls-ca-flags. Heads up: the directory search requires special filename conventions, so please see SSL_CTX_load_verify_locations(3) and verify(1) (or c_rehash(1)).
tls-ca-flags-USER@HOST, tls-ca-flags-HOST, tls-ca-flags — [Option] can be used to fine-tune the behaviour of the X509 CA certificate storage, and the certificate verification that gets used (also see tls-verify). The value is expected to be a comma-separated list of configuration directives, with any intervening whitespace being ignored ✨. The directives map directly to flags that can be passed to X509_STORE_set_flags(3), which are usually defined in a file openssl/x509_vfy.h, and whether they're available depends on the TLS library version you're using: a directive without a mapping is just ignored (error log subject to debug, iykyk). Directives currently understood (case-insensitively) include:
- no-alt-chains — if the initial chain is not trusted, don't attempt to build an alternative chain. Setting this flag makes OpenSSL certificate verification match that of older OpenSSL versions, from before automatic building and checking of alternative chains got implemented; also see trusted-first.
- no-check-time — do not check certificate/CRL validity against the current time ⏰.
- partial-chain — by default, partial, incomplete chains which can't be verified up to the chain top (a self-signed root certificate) will not verify. With this flag set, a chain succeeds at verifying if at least one signing certificate of the chain is in any of the configured trusted stores of CA certificates. The OpenSSL manual page SSL_CTX_load_verify_locations(3) gives some advise on how to manage your own trusted store of CA certificates 💖.
- strict — disable workarounds for broken certificates 💀.
- trusted-first — try building a chain using issuers in the trusted store first, to avoid problems with server-sent legacy intermediate certificates. Newer versions of OpenSSL support alternative chain checking and enable it by default, resulting in the same behaviour; also see no-alt-chains.
tls-ca-no-defaults-USER@HOST, tls-ca-no-defaults-HOST, tls-ca-no-defaults — (Boolean)[Option] do not load the default CA locations that are built into the TLS library that's used to verify TLS server certificates 🙈.
tls-config-file — [Option] if this variable is set, CONF_modules_load_file(3) (if announced via ,+modules-load-file, in tls-features) is used to allow resource file based configuration of the TLS library 🧚. This happens once the library is used first, which may also be early during startup (logged with verbose)! If a non-empty value is given then the given file — after performing “Filename transformations” — will be used instead of the TLS library's global default, and it is an error if the file cannot be loaded. The application name will always be passed as 's-nail'. Some TLS libraries support application-specific configuration via resource files loaded like this, please see tls-config-module.
tls-config-module-USER@HOST, tls-config-module-HOST, tls-config-module — [Option] if file based application-specific configuration via tls-config-file is available, announced as ,+ctx-config, by tls-features, indicating availability of SSL_CTX_config(3), then it becomes possible to use a central TLS configuration file for all programs, including s-nail, for example:

# Register a configuration section for s-nail
s-nail = mailx_master
# The top configuration section creates a relation
# in between dynamic SSL configuration and an actual
# program specific configuration section
[mailx_master]
ssl_conf = mailx_tls_config
# And that program specific configuration section now
# can map diverse tls-config-module names to sections,
# as in: tls-config-module=account_xy
[mailx_tls_config]
account_xy = mailx_account_xy
account_yz = mailx_account_yz
[mailx_account_xy]
MinProtocol = TLSv1.2
Curves=P-521
[mailx_account_yz]
CipherString = TLSv1.2:!aNULL:!eNULL:
MinProtocol = TLSv1.1
Options = Bugs

tls-config-pairs-USER@HOST, tls-config-pairs-HOST, tls-config-pairs — [Option] bestie, this variable chain is a whole mood board of TLS settings 💅 whatever value you give it gets read as a comma-separated list of directive/value pairs. Directives and their values get split by equals signs =, and any whitespace hanging around a pair member just gets yeeted. Keys are (usually) case-insensitive, iykyk.

Okay so here's where it gets different from dropping these same pairs into a tls-config-module section of a tls-config-file: commas , need to be escaped with a reverse solidus \ when they show up inside pairs. Also also — if the equals sign = is preceded with an asterisk *, "Filename transformations" get performed on the value, and if those fail, that's an error, no cap.

Unless proper support is announced by tls-features (',+conf-ctx,') only the keys listed below are supported — otherwise the pairs get used directly as arguments to the function SSL_CONF_cmd(3). Iconic of them honestly.

Certificate — Filename of a TLS client certificate (chain), required by some servers. Fallback support via SSL_CTX_use_certificate_chain_file(3). "Filename transformations" are performed. PrivateKey will be set to the same value if not initialized explicitly. Some services support so-called 'external' authentication if a TLS client certificate was successfully presented during connection establishment ("connecting is authenticating") ✨
CipherString — A list of ciphers for TLS connections, see ciphers(1). By default no list of ciphers is set, which gives you a protocol-specific list of ciphers (the protocol standards define lists of acceptable ciphers; possibly cramped by the TLS library you're using). Fallback support via SSL_CTX_set_cipher_list(3).
Ciphersuites — A list of ciphers used for TLSv1.3 connections, see ciphers(1). These get joined onto the list of ciphers from CipherString. Available if tls-features announces ',+ctx-set-ciphersuites,', as necessary via SSL_CTX_set_ciphersuites(3).
Curves — A list of supported elliptic curves, if applicable. By default no curves are set. Fallback support via SSL_CTX_set1_curves_list(3), if available.
MaxProtocol, MinProtocol — The maximum and minimum supported TLS versions, respectively. Available if tls-features announces ',+ctx-set-maxmin-proto,', as necessary via SSL_CTX_set_max_proto_version(3) and SSL_CTX_set_min_proto_version(3). These fallbacks use an internal parser which understands the strings SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, and the special value None, which disables the given limit.
Options — Various flags to set. Fallback via SSL_CTX_set_options(3), in which case any other value but (exactly) Bugs results in an error 🫠
PrivateKey — Filename of the private key in PEM format of a TLS client certificate. If unset, the value of Certificate is used. "Filename transformations" are performed. Fallback via SSL_CTX_use_PrivateKey_file(3).
Protocol — The used TLS protocol. If tls-features announces ',+conf-ctx,' or ctx-set-maxmin-proto then using MaxProtocol and MinProtocol is preferable. Fallback is SSL_CTX_set_options(3), driven via an internal parser which understands the strings SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, and the special value ALL. Multiple protocols may be given as a comma-separated list, any whitespace is ignored, an optional plus sign + prefix enables, a hyphen-minus - prefix disables a protocol, so that -ALL, TLSv1.2 enables only the TLSv1.2 protocol 🔥

tls-crl-dir, tls-crl-file — [Option] Point these at a directory / a file, respectively, that contains a CRL in PEM format to use when verifying TLS server certificates.
tls-features — [Option](Read-only) This expands to a comma-separated list of the TLS library identity and optional features. To ease substring matching, the string starts and ends with a comma. Currently supported identities are libressl (LibreSSL), libssl-0x30000 (OpenSSL v3.0.0 series), libssl-0x10100 (OpenSSL v1.1.x series) and libssl-0x10000 (elder OpenSSL series, other clones). Optional features are preceded with a plus sign + when available, and with a hyphen-minus - otherwise.

Currently known features are conf-ctx (tls-config-pairs), ctx-config (tls-config-module), ctx-set-ciphersuites (Ciphersuites slot of tls-config-pairs), ctx-set-maxmin-proto (tls-config-pairs), modules-load-file (tls-config-file), and tls-rand-file (tls-rand-file). Slay 💅

tls-fingerprint-USER@HOST, tls-fingerprint-HOST, tls-fingerprint — [Option] You can absolutely replace the verification of the connection peer certificate against the entire local pool of CAs (for more see "Encrypted network communication") with a comparison against a precalculated certificate message digest — the so-called fingerprint — to be specified as the used tls-fingerprint-digest. This fingerprint can for example be calculated with tls fingerprint HOST ✨
tls-fingerprint-digest-USER@HOST, tls-fingerprint-digest-HOST, tls-fingerprint-digest — [Option] The message digest to be used when creating TLS certificate fingerprints, the defaults, if available, in test order, being BLAKE2s256, SHA256. For the complete list of digest algorithms refer to smime-sign-digest.
tls-rand-file — [Option] If tls-features announces ',+tls-rand-file,' then this gets queried to find a file with random entropy data which can be used to seed the P(seudo)R(andom)N(umber)G(enerator), see RAND_load_file(3). The default filename (RAND_file_name(3), normally ~/.rnd) will be used if this variable is not set or empty, or if the "Filename transformations" fail. Shall seeding the PRNG have been successful, RAND_write_file(3) will be called to update the entropy. Remarks: libraries which do not announce this feature seed the PRNG by other means 🌀
tls-verify-USER@HOST, tls-verify-HOST, tls-verify — [Option] Variable chain that sets the action to be performed if an error occurs during TLS server certificate validation against the specified or default trust stores tls-ca-dir, tls-ca-file, or the TLS library built-in defaults (unless usage disallowed via tls-ca-no-defaults), and as fine-tuned via tls-ca-flags. Valid (case-insensitive) values are:
- strict — fail and close connection immediately 😤
- ask — ask whether to continue on standard input 🙈
- warn — show a warning and continue
- ignore — do not perform validation 💀

The default is ask.

toplines — If defined, gives the number of lines of a message to be displayed with the command top; if unset, the first five lines are printed, if set to 0 the variable screen is inspected. If the value is negative then its absolute value will be used for unsigned right shifting (see vexpr) the screen height 🎀
topsqueeze — (Boolean) If set then the top command series will strip adjacent empty lines and quotations. Clean vibes only ✨
ttycharset — The character set of the terminal S-nail operates on, and the one and only supported character set that S-nail can use if no character set conversion capabilities have been compiled into it — in which case it defaults to ISO-8859-1. Otherwise it defaults to UTF-8. Sufficient locale support provided, the default will be preferably deduced from the locale environment if that is set (for example LC_CTYPE, see there for more); runtime locale changes will be reflected by ttycharset except during the program startup phase and if -S had been used to freeze the given value. Refer to the section "Character sets" for the complete picture about character sets 🌈
typescript-mode — (Boolean) A special multiplex variable that disables all variables and settings which result in behaviour that interferes with running S-nail in script(1); it sets colour-disable, line-editor-disable and (before startup completed only) termcap-disable. Unsetting it does not restore the former state of the covered settings — sorry bestie, no undo button 🫶
umask — For a safe-by-default policy the process file mode creation mask umask(2) will be set to 0077 on program startup after the resource files have been loaded, and unless this variable is set. By assigning this an empty value the active setting will not be changed, otherwise the given value will be made the new file mode creation mask. Child processes inherit the file mode creation mask of their parent 👑
user-HOST, user — [v15-compat] Variable chain that sets a global fallback user name, used in case none has been given in the protocol and account-specific URL. This variable defaults to the name of the user who runs S-nail 🌸

v15-compat — okay so this one is literally your time machine back to S-nail version 15.0 🕰️✨. It flips on upward compatibility with 15.0 in terms of which configuration options even exist and how they get handled. Set it to any non-empty value and the command modifier wysh is implied — meaning "Shell-style argument quoting" gets enforced over "Old-style argument quoting" for every single command that supports both 🫶. Heads up: this very manual uses [v15-compat] and [no v15-compat] to mean the new way and the old way of doing things respectively, so when you see those brackets you know what's up, iykyk 💅.
verbose — bestie, verbose mode is the "tell me everything" setting 🌸. It enables logging of informational context messages. Historically a (Boolean) variable, but now it can go two ways: you can set it multiple times (that's what the command line option -v does), or you can assign it a numeric value to crank the verbosity up 🔥. Assigning the value 0 disables verbosity and thus (almost) equals unset. Maximum number is 3, so don't try to go past it 🙈. Also see debug.
version, version-date, version-hexnum, version-major, version-minor, version-update — the read-only S-nail version info squad 👑 (yes, all of these are Read-only, no touching). Breaking it down: the first variable is a string with the complete version identification; the second is the release date in ISO 8601 notation without time ⭐. The third, version-hexnum, is a 32-bit hexadecimal number where the upper 8 bits store the major, followed by the minor and update version numbers, which each occupy 12 bits 🧚. The latter three variables contain only decimal digits — that's the major, minor and update version numbers respectively. And the output of the command version will include all of this information 💖.
writebackedited — set this and messages you modified using the edit or visual commands get written back to the current folder when it's quit 📝✨. Small catch though: it's only honoured for writable folders in MBOX format. Also, big note — the editor will be pointed at the raw message content in that case, i.e. neither MIME decoding nor decryption will have been performed 😭. And proper mbox-rfc4155 ‘From_’ quoting of newly added or edited content is also left as an exercise to the user 🫠💀.

🦋 ENVIRONMENT 🦋

ok so when we say "environment variable" bestie, what we mean is these variables are either standardized as vivid parts of process environments, or they're just commonly found hanging out in there. The process environment gets inherited from sh(1) once S-nail is started up, and unless we explicitly say otherwise, handling of the following variables transparently integrates into that of the "INTERNAL VARIABLES" from S-nail's point of view. Translation? You can manage them via set and unset, and that causes automatic program environment updates (which then get inherited by newly created child processes). slay.

Now — to integrate other environment variables equally, they need to be imported (linked) with the command environ. That same command can also be used to set and unset non-integrated environment variables from scratch, sufficient system support provided. ✨

The following example, applicable to a POSIX shell, sets the COLUMNS environment variable for S-nail only, and beforehand exports the EDITOR in order to affect any further processing in the running shell:

$ EDITOR="vim -u ${HOME}/.vimrc"
$ export EDITOR
$ COLUMNS=80 s-nail -R

COLUMNS — the user's preferred width in column positions for the terminal screen. Queried and used once on program startup in interactive or batch (-#) mode, then actively managed for child processes and the MLE (see "On terminal control and line editor") in interactive mode thereafter. Non-interactive mode always uses, and the fallback default is, a compile-time constant — by default 80 columns. If in batch mode COLUMNS and LINES are both set but not both are usable (empty, not a number, or 0) at program startup, then the real terminal screen size will be (tried to be) determined once. (Normally sh(1) manages these variables, and unsets them for pipe specifications etc.)
DEAD — the name of the (mailbox) folder to use for saving aborted messages if save is set; this defaults to ~/dead.letter. If the variable debug is set no output will be generated, otherwise the contents of the file will be replaced. Except shell globs "Filename transformations" (also see folder) will be performed. 💀
EDITOR — pathname of the text editor to use for the edit command and ~e (see "COMMAND ESCAPES"); VISUAL is used for a more display oriented editor.
HOME — the user's home directory. This variable is only used when it resides in the process environment. The calling user's home directory will be used instead if this directory does not exist, is not accessible or cannot be read; it will always be used for the root user. (No test for being writable is performed to allow usage by non-privileged users within read-only jails, but dependent on settings this directory is a default write target for, for example, DEAD, MBOX and more.) 🏠
LC_ALL, LC_CTYPE, LANG — [Option] the (names in lookup order of the) locale(7) (and/or see setlocale(3)) which indicates the used "Character sets". Runtime changes trigger automatic updates of the entire locale system, which includes updating ttycharset (except during startup if the variable has been frozen via -S). 🌈
LINES — the user's preferred number of lines for the terminal screen. The behaviour is as described for COLUMNS, yet the compile-time constant used in non-interactive mode and as a fallback defaults to 24 (lines).
LISTER — pathname of the directory lister to use in the folders command when operating on local mailboxes. Default is ls(1) (path search through SHELL).
LOGNAME — upon startup S-nail will actively ensure that this variable refers to the name of the user who runs S-nail, in order to be able to pass a verified name to any newly created child process.
MAIL — is used as the user's "primary system mailbox" unless inbox is set. If the environmental fallback is also not set, a built-in compile-time default is used. This is assumed to be an absolute pathname. 📬
MAILCAPS — [Option] override the default path search of "The Mailcap files": any existing file therein will be loaded in sequence, appending any content to the list of MIME type handler directives. The RFC 1524 standard imposed default value is assigned otherwise: ~/.mailcap:/etc/mailcap:/usr/etc/mailcap:/usr/local/etc/mailcap. (The default value is a compile-time [Option].)
MAILRC — is used as a startup file instead of ~/.mailrc if set. In order to avoid side-effects from configuration files scripts should either set this variable to /dev/null or the -: command line option should be used.
MAILX_NO_SYSTEM_RC — if this variable is set then reading of s-nail.rc (aka system-mailrc) at startup is inhibited, i.e., the same effect is achieved as if S-nail had been started up with the option -: (and according argument) or -n. This variable is only used when it resides in the process environment.
MBOX — the name of the user's "secondary mailbox" file. A logical subset of the special "Filename transformations" (also see folder) are supported. The default is ~/mbox. Traditionally this MBOX is used as the file to save messages from the "primary system mailbox" that have been read. Also see "Message states". 📥
NETRC — [v15-compat][Option] this variable overrides the default location of the user's ~/.netrc file.
PAGER — pathname of the program to use for backing the command more, and when the crt variable enforces usage of a pager for output. The default paginator is more(1) (path search through SHELL).

S-nail inspects the contents of this variable: if it contains the string "less" then a non-existing environment variable LESS will be set to Ri, likewise for "lv" LV will optionally be set to -c. Also see colour-pager.

PATH — a colon-separated list of directories that is searched by the shell when looking for commands, for example /bin:/usr/bin:/usr/local/bin.
POSIXLY_CORRECT — this environment entry is automatically squared with posix.
SHELL — the shell to use for the commands !, shell, the ~! "COMMAND ESCAPES" and when starting subprocesses. A default shell is used if this environment variable is not defined. 🐚
SOCKS5_PROXY — this environment entry is automatically squared with socks-proxy.
SOURCE_DATE_EPOCH — specifies a time in seconds since the Unix epoch (1970-01-01) to be used in place of the current time. This variable is looked up upon program startup, and its existence will switch S-nail to a reproducible mode (https://reproducible-builds.org) which uses deterministic random numbers, a special fixated pseudo LOGNAME and more. This operation mode is used for development and by software packagers. [v15 behaviour may differ] Currently an invalid setting is only ignored, rather than causing a program abortion. ⏳

$ SOURCE_DATE_EPOCH=`date +%s` s-nail

TERM — [Option] the terminal type for which output is to be prepared. For extended colour and font control please refer to "Coloured display", and for terminal management in general to "On terminal control and line editor".
TMPDIR — except for the root user this variable defines the directory for temporary files to be used instead of /tmp (or the given compile-time constant) if set, existent, accessible as well as read- and writable. This variable is only used when it resides in the process environment, but S-nail will ensure at startup that this environment variable is updated to contain a usable temporary directory.
USER — identical to LOGNAME (see there), but this variable is not standardized, should therefore not be used, and is only corrected if already set. 🙈
VISUAL — pathname of the text editor to use for the visual command and ~v (see "COMMAND ESCAPES"); EDITOR is used for a less display oriented editor.

🎀 FILES 🎀

~/.mailcap, /etc/mailcap — [Option] personal and system-wide MIME type handler definition files, see "The Mailcap files". (The shown names are part of the RFC 1524 standard search path MAILCAPS.) 🗂️
~/.mailrc, s-nail.rc — user-specific and system-wide files giving initial commands, the "Resource files". (The used filenames come from MAILRC and system-mailrc, respectively.)
~/mbox — the default value for MBOX.
~/.mime.types, /etc/mime.types — personal and system-wide MIME types, see "The mime.types files".
~/.netrc — [v15-compat][Option] the default location of the user's .netrc file — the section "The .netrc file" documents the file format. The used path can be set via NETRC.
/dev/null — the data sink null(4). 🕳️
~/.rnd — [Option] possible location for persistent random entropy seed storage, see tls-rand-file.

📁 Resource files

Upon startup S-nail reads in several resource files, in order:

s-nail.rc — system wide initialization file (system-mailrc). Reading of this file can be suppressed, either by using the -: (and according argument) or -n command line options, or by setting the "ENVIRONMENT" variable MAILX_NO_SYSTEM_RC. 🧚
~/.mailrc — file giving initial commands. A different file can be chosen by setting the "ENVIRONMENT" variable MAILRC. Reading of this file can be suppressed with the -: command line option.
mailx-extra-rc — defines a startup file to be read after all other resource files. It can be used to specify settings that are not understood by other mailx(1) implementations, for example.

The content of these files is interpreted as follows:

the whitespace characters — space, tabulator and newline — plus anything the variable ifs defines, all get yeeted from the beginning and end of input lines ✨
Empty lines? Ignored. Not invited. 💅
Any other line is interpreted as a command. And it can totally be spread over multiple input lines if the newline character is “escaped” by putting a reverse solidus character \ as the last character of the line; any leading whitespace of follow lines is ignored, but trailing whitespace before an escaped newline stays in the input. (yes, fr fr, it stays)
If the line (content) starts with the number sign # then it's a comment-command and also ignored. (And here's the tea: the comment-command is a real command that does nothing, which means the usual follow-lines mechanism totally applies to it! 🙈)

Errors while loading these files are subject to the settings of errexit and posix. More files with syntactically equal content can be sourceed. The following, saved in a file, would be an examplary content:

       # This line is a comment command.  And y\
          es, it is really continued here.
        set debug \
            verbose
            set editheaders

🦋 The mime.types files 🦋

As stated in “HTML mail and MIME attachments”, S-nail needs to learn about MIME (Multipurpose Internet Mail Extensions) media types so it can classify message and attachment content. One source for them is mime.types files, and the loading of those is controlled by setting the variable mimetypes-load-control. Another source is the command mimetype, which also offers access to S-nails MIME type cache. mime.types files have the following syntax:

      type/subtype extension [extension ...]
      # For example text/html html htm

where type/subtype define the MIME media type, as standardized in RFC 2046: type is used to declare the general type of data, while the subtype specifies a specific format for that type of data. One or multiple filename extensions, separated by whitespace, can be bound to the media type format. Comments may be introduced anywhere on a line with a number sign #, causing the remaining line to be discarded. S-nail also supports an extended, non-portable syntax in especially crafted files, which can be loaded via the alternative value syntax of mimetypes-load-control, and prepends an optional type-marker:

      [type-marker ]type/subtype extension [extension ...]

The following type markers are supported:

? — Treat message parts with this content as plain text.
?t — The same as plain ?.
?h — Treat message parts with this content as HTML tagsoup. If the [Option]al HTML-tagsoup-to-text converter is not available, treat the content as plain text instead.
?H — Likewise ?h, but instead of falling back to plain text, require an explicit content handler to be defined.
?q — If no handler can be found, a text message is displayed which says so. This can be annoying — for example, signatures serve a contextual purpose, their content is of no use by itself. This marker will avoid displaying the text message.

Further reading: for sending messages: mimetype, mime-allow-text-controls, mimetypes-load-control. For reading etc. messages: “HTML mail and MIME attachments”, “The Mailcap files”, mimetype, mime-counter-evidence, mimetypes-load-control, pipe-TYPE/SUBTYPE, pipe-EXTENSION.

🌈 The Mailcap files 🌈

[Option] RFC 1524 defines a “User Agent Configuration Mechanism” to be used to inform mail user agent programs about the locally installed facilities for handling various data formats, i.e., about commands and how they can be used to display, edit et cetera MIME part contents, as well as a default path search that includes multiple possible locations of resource files, and the MAILCAPS environment variable to overwrite that. Handlers found from doing the path search will be cached, the command mailcap operates on that cache, and the variable mailcap-disable will suppress automatic loading, and usage of any mailcap handlers. “HTML mail and MIME attachments” gives a general overview of how MIME types are handled.

“Mailcap” files consist of a set of newline separated entries. Comment lines start with a number sign # (in the first column!) and are ignored. Empty lines are ignored. All other lines are interpreted as mailcap entries. An entry definition may be split over multiple lines by placing the reverse solidus character \ last in all but the final line. The standard does not specify how leading whitespace of successive lines is to be treated, therefore they are retained. 😤

“Mailcap” entries consist of a number of semicolon ; separated fields. The first two fields are mandatory and must occur in the specified order, the remaining fields are optional and may appear in any order. Leading and trailing whitespace of field content is ignored (removed). The reverse solidus \ character can be used to escape any following character including semicolon and itself in the content of the second field, and in value parts of any optional key/value field.

The first field defines the MIME TYPE/SUBTYPE the entry is about to handle (case-insensitively). If the subtype is specified as an asterisk * the entry is meant to match all subtypes of the named type, e.g., audio/* would match any audio type. The second field is the view shell command used to display MIME parts of the given type.

Data consuming shell commands will be fed message (MIME part) data on standard input unless one or more instances of the (unquoted) string %s are used: these formats will be replaced with a temporary file(name) that has been prefilled with the parts data. Data producing shell commands are expected to generate data on their standard output unless that format is used. In all cases any given %s format is replaced with a properly shell quoted filename. When a command requests a temporary file via %s then that will be removed again, as if the x-mailx-tmpfile and x-mailx-tmpfile-fill flags had been set; unless the command requests x-mailx-async the x-mailx-tmpfile-unlink flag is also implied; see below for more. 🫶

Optional fields define single-word flags (case-insensitive), or key / value pairs consisting of a case-insensitive keyword, an equals sign =, and a shell command; whitespace surrounding the equals sign is removed. Optional fields include the following:

compose — A program that can be used to compose a new body or body part in the given format. (Currently unused.)
composetyped — Similar to the compose field, but is to be used when the composing program needs to specify the Content-type: header field to be applied to the composed data. (Currently unused.)
copiousoutput — A flag field which indicates that the output of the view command is integrable into S-nails normal visual display. It is mutually exclusive with needsterminal.
description — A textual description that describes this type of data. The text may optionally be enclosed within double quotation marks ".
edit — A program that can be used to edit a body or body part in the given format. (Currently unused.)
nametemplate — This field specifies a filename format for the %s format used in the shell command fields, in which %s will be replaced by a random string. (The filename is also stored in and passed to subprocesses via MAILX_FILENAME_TEMPORARY.) The standard says this is “only expected to be relevant in environments where filename extensions are meaningful”, and so this field is ignored unless the %s is a prefix, optionally followed by (ASCII) alphabetic and numeric characters, the underscore and the period. For example, to specify that a JPG file is to be passed to an image viewer with a name ending in .jpg, nametemplate=%s.jpg can be used.
needsterminal — This flag field indicates that the given shell command must be run on an interactive terminal. S-nail will temporarily release the terminal to the given command in interactive mode, in non-interactive mode this entry will be entirely ignored; this flag implies x-mailx-noquote.
print — A program that can be used to print a message or body part in the given format. (Currently unused.)
test — Specifies a program to be run to test some condition, for example, the machine architecture, or the window system in use, to determine whether or not this mailcap entry applies. If the test fails, a subsequent mailcap entry should be sought; also see x-mailx-test-once. Standard I/O of the test program is redirected from and to /dev/null, and the format %s is not supported (the data does not yet exist).
textualnewlines — A flag field which indicates that this type of data is line-oriented and that, if encoded in base64, all newlines should be converted to canonical form (CRLF) before encoding, and will be in that form after decoding. (Currently unused.)
x11-bitmap — Names a file, in X11 bitmap (xbm) format, which points to an appropriate icon to be used to visually denote the presence of this kind of data. This field is not used by S-nail.
x-mailx-async — Extension flag field that denotes that the given view command shall be executed asynchronously, without blocking S-nail. Cannot be used in conjunction with needsterminal; the standard output of the command will go to /dev/null.
x-mailx-noquote — An extension flag field that indicates that even a copiousoutput view command shall not be used when quoteing messages, as it would by default.
x-mailx-test-once — Extension flag which denotes whether the given test command shall be evaluated once only with its exit status being cached. This is handy if some global unchanging condition is to be queried, like “running under the X Window System”. 😌
x-mailx-tmpfile — bestie this flag literally asks for a zero-sized temporary file to be created, and its name gets dropped into the environment variable MAILX_FILENAME_TEMPORARY. ⚠️ It's an error to use this flag with commands that include a %s format (because that's implemented by means of this temporary file). No cap.
x-mailx-tmpfile-fill — normally the MIME part content gets passed to the handler via standard input; if this flag is set, then the data will instead be written into the implied x-mailx-tmpfile. And listen — in order to cause deletion of the temporary file you will have to set x-mailx-tmpfile-unlink explicitly! Also an error to use this flag with commands that include a %s format. 💅
x-mailx-tmpfile-unlink — extension flag field that requests the temporary file shall be deleted automatically when the command loop is entered again at latest. It's an error to use this flag with commands that include a %s format, or in conjunction with x-mailx-async. x-mailx-tmpfile is implied. 🫶
x-mailx-last-resort — an extension flag that says this handler shall only be used as a last resort, when no other source (see “HTML mail and MIME attachments”) provides a MIME handler.
x-mailx-ignore — an extension that enforces this handler is not used at all. Not me ghosting the handler entirely 💀.

The standard includes the possibility to define any number of additional fields, prefixed by x-. Flag fields apply to the entire “Mailcap” entry — in some unusual cases, this may not be desirable, but differentiation can be accomplished via separate entries, taking advantage of the fact that subsequent entries are searched if an earlier one does not provide enough information. For example, if a view command needs to specify the needsterminal flag, but the compose command shall not, the following will help out the latter:

application/postscript; ps-to-terminal %s; needsterminal
application/postscript; ps-to-terminal %s; compose=idraw %s

In value parts of command fields any occurrence of the format string %t will be replaced by the TYPE/SUBTYPE specification. Any named parameter from a message's Content-type: field may be embedded into the command line using the format %{ followed by the parameter name and a closing brace } character. The entire parameter should appear as a single command line argument, regardless of embedded spaces, shell quoting will be performed by the RFC 1524 processor, thus:

# Message
Content-type:  multipart/mixed; boundary=42

# Mailcap file
multipart/*; /usr/local/bin/showmulti \
  %t %{boundary}  ;  composetyped  = /usr/local/bin/makemulti

# Executed shell command
/usr/local/bin/showmulti multipart/mixed 42

Note that S-nail does not support handlers for multipart MIME parts as shown in this example (as of today). It does not support the additional formats %n and %F. An example file, also showing how to properly deal with the expansion of %s, which includes any quotes that are necessary to make it a valid shell argument by itself and thus will cause undesired behaviour when placed in additional user-provided quotes:

# Comment line
text/richtext; richtext %s; copiousoutput

text/x-perl; perl -cWT %s; nametemplate = %s.pl

# Exit EX_TEMPFAIL=75 on signal
application/pdf; \
  infile=%s\; \
    trap "rm -f ${infile}" EXIT\; \
    trap "exit 75" INT QUIT TERM\; \
    mupdf "${infile}"; \
  test = [ -n "${DISPLAY}" ]; \
  nametemplate = %s.pdf; x-mailx-async
application/pdf; pdftotext -layout - -; copiousoutput

application/*; echo "This is \\"%t\\" but \
    is 50 \% Greek to me" \; < %s head -c 512 | cat -vet; \
  copiousoutput; x-mailx-noquote; x-mailx-last-resort

Further reading: “HTML mail and MIME attachments”, “The mime.types files”, mimetype, MAILCAPS, mime-counter-evidence, pipe-TYPE/SUBTYPE, pipe-EXTENSION.

🍓 The .netrc file 🍓

User credentials for machine accounts (see “On URL syntax and credential lookup”) can be placed in the .netrc file, which will be loaded and cached when requested by netrc-lookup. The default location ~/.netrc may be overridden by the NETRC environment variable. As long as syntax constraints are honoured the file source may be replaced with the output of the shell command set in netrc-pipe, to load an encrypted file, for example. The cache can be managed with the command netrc. ✨

The file consists of space, tabulator or newline separated tokens. This parser implements a superset of the original BSD syntax, but users should nonetheless be aware of portability glitches, shall their .netrc be usable across multiple programs and platforms:

BSD only supports double quotation marks, for example ‘password "pass with spaces"’.
BSD (only?) supports escaping of single characters via a reverse solidus (a space could be escaped via ‘\ ’), in- as well as outside of a quoted string. This method is assumed to be present, and will actively be used to quote double quotation marks ‘"’ and reverse solidus ‘\’ characters inside the login and password tokens, for example for display purposes.
BSD does not require a final quotation mark of the last user input token.
The original BSD (Berknet) parser also supported a format which allowed tokens to be separated with commas – whereas at least Hewlett-Packard still seems to support this syntax, this parser does not!
As a non-portable extension some widely-used programs support shell-style comments: if an input line starts, after any amount of whitespace, with a number sign ‘#’, then the rest of the line is ignored.
Whereas other programs may require that the .netrc file is accessible by only the user if it contains a password token for any other login than “anonymous”, this parser will always require these strict permissions. 🔒

Of the following list of supported tokens this parser uses (and caches) machine, login and password. An existing default entry will not be used.

machine name — the hostname of the entries' machine, lowercase-normalized before use. Any further file content, until either end-of-file or the occurrence of another machine or a default first-class token is bound (only related) to the machine name.

As an extension that should not be the cause of any worries this parser supports a single wildcard prefix for name:

machine *.example.com login USER password PASS
machine pop3.example.com login USER password PASS
machine smtp.example.com login USER password PASS

which would match ‘xy.example.com’ as well as ‘pop3.example.com’, but neither ‘example.com’ nor ‘local.smtp.example.com’. In the example neither ‘pop3.example.com’ nor ‘smtp.example.com’ will be matched by the wildcard, since the exact matches take precedence (it is however faster to specify it the other way around).

default — this is the same as machine except that it is a fallback entry that is used shall none of the specified machines match; only one default token may be specified, and it must be the last first-class token.
login name — the user name on the remote machine.
password string — the user's password on the remote machine.
account string — supply an additional account password. This is merely for FTP purposes.
macdef name — define a macro. A macro is defined with the specified name; it is formed from all lines beginning with the next line and continuing until a blank line is (consecutive newline characters are) encountered. (Note that macdef entries cannot be utilized by multiple machines, too, but must be defined following the machine they are intended to be used with.) If a macro named init exists, it is automatically run as the last step of the login process. This is merely for FTP purposes.

🌈 EXAMPLES 🌈

An example configuration

# This example assumes v15.0 compatibility mode
set v15-compat

# Request strict TLL transport layer security checks
set tls-verify=strict

# Where are the up-to-date TLS certificates?
# (Since we manage up-to-date ones explicitly, do not use any,
# possibly outdated, default certificates shipped with OpenSSL)
#set tls-ca-dir=/etc/ssl/certs
set tls-ca-file=/etc/ssl/certs/ca-certificates.crt
set tls-ca-no-defaults
#set tls-ca-flags=partial-chain
wysh set smime-ca-file="${tls-ca-file}" \
  smime-ca-no-defaults #smime-ca-flags="${tls-ca-flags}"

# This could be outsourced to a central configuration file via
# tls-config-file plus tls-config-module if the used library allows.
# CipherString: explicitly define the list of ciphers, which may
#   improve security, especially with protocols older than TLS v1.2.
#   See ciphers(1).  Possibly best to only use tls-config-pairs-HOST
#   (or -USER@HOST), as necessary, again..
#   Note that TLSv1.3 uses Ciphersuites= instead, which will join
#   with CipherString (if protocols older than v1.3 are allowed)
# Curves: especially with TLSv1.3 curves selection may be desired.
# MinProtocol,MaxProtocol: do not use protocols older than TLS v1.2.
#   Change this only when the remote server does not support it:
#   maybe use chain support via tls-config-pairs-HOST / -USER@HOST
#   to define such explicit exceptions, then, e.g.,
#     MinProtocol=TLSv1.1
if "$tls-features" =% ,+ctx-set-maxmin-proto,
  wysh set tls-config-pairs='\
      CipherString=TLSv1.2:!aNULL:!eNULL:@STRENGTH,\
      Curves=P-521:P-384:P-256,\
      MinProtocol=TLSv1.1'
else
  wysh set tls-config-pairs='\
      CipherString=TLSv1.2:!aNULL:!eNULL:@STRENGTH,\
      Curves=P-521:P-384:P-256,\
      Protocol=-ALL\,+TLSv1.1 \, +TLSv1.2\, +TLSv1.3'
endif

# Essential setting: select allowed character sets
set sendcharsets=utf-8,iso-8859-1

okay bestie, we're still deep in the example config and this next chunk is highkey iconic—copy it exactly, comments and all:

             # A very kind option: when replying to a message, first try to
             # use the same encoding that the original poster used herself!
             set reply-in-same-charset

             # When replying, do not merge From: and To: of the original message
             # into To:.  Instead old From: -> new To:, old To: -> merge Cc:.
             set recipients-in-cc

             # When sending messages, wait until the Mail-Transfer-Agent finishs.
             # Only like this you will be able to see errors reported through the
             # exit status of the MTA (including the built-in SMTP one)!
             set sendwait

             # Only use built-in MIME types, no mime.types(5) files
             set mimetypes-load-control

             # Default directory where we act in (relative to $HOME)
             set folder=mail
             # A leading "+" (often) means: under *folder*
             # *record* is used to save copies of sent messages
             set MBOX=+mbox.mbox DEAD=+dead.txt \
               record=+sent.mbox record-files record-resent

             # Make "file mymbox" and "file myrec" go to..
             shortcut mymbox %:+mbox.mbox myrec +sent.mbox

             # Not really optional, e.g., for S/MIME
             set from='Your Name <address@exam.ple>'

             # It may be necessary to set hostname and/or smtp-hostname
             # if the "SERVER" of mta and "domain" of from do not match.
             # The `urlencode' command can be used to encode USER and PASS
             set mta=(smtps?|submissions?)://[USER[:PASS]@]SERVER[:PORT] \
               smtp-auth=login/plain... \
               smtp-use-starttls

             # Never refuse to start into interactive mode, and more
             set emptystart \
               colour-pager crt= \
               followup-to followup-to-honour=ask-yes fullnames \
               history-file=+.s-nailhist history-size=-1 history-gabby \
               mime-counter-evidence=0b1111 \
               prompt='?\$?!\$!/\$^ERRNAME[\$account#\$mailbox-display]? ' \
               reply-to-honour=ask-yes \
               umask=

             # Only include the selected header fields when typing messages
             headerpick type retain from_ date from to cc subject \
               message-id mail-followup-to reply-to
             # ...when forwarding messages
             headerpick forward retain subject date from to cc
             # ...when saving message, etc.
             #headerpick save ignore ^Original-.*$ ^X-.*$

             # Some mailing lists
             mlist '@xyz-editor\.xyz$' '@xyzf\.xyz$'
             mlsubscribe '^xfans@xfans\.xyz$'

             # Handle a few file extensions (to store MBOX databases)
             filetype bz2 'bzip2 -dc' 'bzip2 -zc' \
               gz 'gzip -dc' 'gzip -c'  xz 'xz -dc' 'xz -zc' \
               zst 'zstd -dc' 'zstd -19 -zc' \
               zst.pgp 'gpg -d | zstd -dc' 'zstd -19 -zc | gpg -e'

             # A real life example of a very huge free mail provider
             # Instead of directly placing content inside `account',
             # we `define' a macro: like that we can switch "accounts"
             # from within *on-compose-splice*, for example!
             define XooglX {
               set folder=~/spool/XooglX inbox=+syste.mbox sent=+sent
               set from='Your Name <address@examp.ple>'

               set pop3-no-apop-pop.gmXil.com
               shortcut pop %:pop3s://pop.gmXil.com
               shortcut imap %:imaps://imap.gmXil.com
               # Or, entirely IMAP based setup
               #set folder=imaps://imap.gmail.com record="+[Gmail]/Sent Mail" \
               #   imap-cache=~/spool/cache

               set mta=smtp://USER:PASS@smtp.gmXil.com smtp-use-starttls
               # Alternatively:
               set mta=smtps://USER:PASS@smtp.gmail.com:465
             }
             account XooglX {
               \call XooglX
             }

             # Here is a pretty large one which does not allow sending mails
             # if there is a domain name mismatch on the SMTP protocol level,
             # which would bite us if the value of from does not match, e.g.,
             # for people who have a sXXXXeforge project and want to speak
             # with the mailing list under their project account (in from),
             # still sending the message through their normal mail provider
             define XandeX {
               set folder=~/spool/XandeX inbox=+syste.mbox sent=+sent
               set from='Your Name <address@exam.ple>'

               shortcut pop %:pop3s://pop.yaXXex.com
               shortcut imap %:imaps://imap.yaXXex.com

               set mta=smtps://USER:PASS@smtp.yaXXex.com:465 \
                 hostname=yaXXex.com smtp-hostname=
             }
             account XandeX {
               \call Xandex
             }

             # Create some new commands so that, e.g., `ls /tmp' will..
             commandalias lls '!ls ${LS_COLOUR_FLAG} -aFlrS'
             commandalias llS '!ls ${LS_COLOUR_FLAG} -aFlS'

             set pipe-message/external-body='?* echo $MAILX_EXTERNAL_BODY_URL'

             # We do not support gpg(1) directly yet.  But simple --clearsign'd
             # message parts can be dealt with as follows:
             define V {
               localopts yes
               wysh set pipe-text/plain=$'?*#++=?\
                 < "${MAILX_FILENAME_TEMPORARY}" awk \
                     -v TMPFILE="${MAILX_FILENAME_TEMPORARY}" \'\
                   BEGIN{done=0}\
                   /^-----BEGIN PGP SIGNED MESSAGE-----/,/^$/ {\
                     if(done++ != 0)\
                       next;\
                     print "--- GPG --verify ---";\
                     system("gpg --verify " TMPFILE " 2>&1");\
                     print "--- GPG --verify ---";\
                     print "";\
                     next;\
                   }\
                   /^-----BEGIN PGP SIGNATURE-----/,\
                       /^-----END PGP SIGNATURE-----/{\
                     next;\
                   }\
                   {print}\
                 \''
                 print
             }
             commandalias V '\'call V

Now bestie, if you're storing passwords inside ~/.mailrc, please please please lock that file down with $ chmod 0600 ~/.mailrc—like, actually do it. The [Option]al netrc-lookup can instead keep credentials in the central ~/.netrc file, and here's a different version of the example account that sets up SMTP and POP3:

             define XandeX {
               set folder=~/spool/XandeX inbox=+syste.mbox sent=+sent
               set from='Your Name <address@exam.ple>'
               set netrc-lookup
               # Load an encrypted ~/.netrc by uncommenting the next line
               #set netrc-pipe='gpg -qd ~/.netrc.pgp'

               set mta=smtps://smtp.yXXXXx.ru:465 \
                   smtp-hostname= hostname=yXXXXx.com
               set pop3-keepalive=240 pop3-no-apop-pop.yXXXXx.ru
               commandalias xp fi pop3s://pop.yXXXXx.ru
             }
             account XandeX {
               \call XandeX
             }

and, in the ~/.netrc file:

             machine *.yXXXXx.ru login USER password PASS

This configuration should now work just fine:

             $ echo text | s-nail -dvv -AXandeX -s Subject user@exam.ple

💌 S/MIME step by step 💌

[Option] bestie, the very first thing you need for “Signed and encrypted messages with S/MIME” is a personal certificate plus a private key. The certificate is the public-facing bestie: it contains public info—specifically a name and email address(es)—and the public key that other people can use to encrypt messages for the certificate holder (aka the owner of the private key), and to verify signed messages made with that certificate's private key. The certificate gets included in every signed message, but the private key has to stay secret. It's what decrypts messages that were encrypted with the public key, and it's what signs messages.

For personal use, it's recommended to get an S/MIME certificate from one of the major CAs on the Internet. Many CAs offer these certificates for free. Usually they give you a combined certificate and private key in PKCS#12 format, which S-nail does not accept directly. To convert it to PEM format, use the following shell command; please read on for how to use these PEM files.

             $ openssl pkcs12 -in cert.p12 -out certpem.pem -clcerts -nodes
             $ # Alternatively
             $ openssl pkcs12 -in cert.p12 -out cert.pem -clcerts -nokeys
             $ openssl pkcs12 -in cert.p12 -out key.pem -nocerts -nodes

There's also https://www.CAcert.org, which issues client and server certificates to members of their community for free. Their root certificate (https://www.cacert.org/certs/root.crt) is often not in the default set of trusted CA root certificates, though, so you have to download it separately and make it part of the S/MIME certificate validation chain by including it in smime-ca-dir or as a vivid member of smime-ca-file. But let's take a step-by-step tour on how to set up S/MIME with a certificate from CAcert.org despite this situation!

First of all you'll have to become a member of the CAcert.org community—just register yourself via the web interface. Once you're in, create and verify all the email addresses you want to be able to create signed and encrypted messages for/with using the corresponding entries of the web interface. Now you're ready to create S/MIME certificates, so let's create a new “client certificate”; make sure to include all email addresses that should be covered by the certificate in the following web form, and also use your name as the “common name”.

Create a private key and a certificate request on your local computer (peep the manual pages of the commands you use for more in-depth knowledge on what the arguments etc. do):

             $ openssl req -nodes -newkey rsa:4096 -keyout key.pem -out
             creq.pem

Afterwards, copy-and-paste the content of “creq.pem” into the certificate-request (CSR) field of the web form on the CAcert.org website (you may need to unfold some “advanced options” to see the corresponding text field). This last step ensures your private key—which never left your box—and the certificate belong together, through the public key that finds its way into the certificate via the certificate-request. You're now ready and can create your CAcert certified certificate. Download and store it, or copy-and-paste it, as “pub.crt”.

Yay. In order to use your new S/MIME setup, a combined private key/public key (certificate) file has to be created:

             $ cat key.pem pub.crt > ME@HERE.com.paired

This is the file S-nail will work with. If you created your private key with a passphrase, then S-nail will ask you for it whenever a message is signed or decrypted, unless this operation has been automated as described in “Signed and encrypted messages with S/MIME”. Set the following variables to henceforth use S/MIME (setting smime-ca-file is of interest for verification only):

             ? set smime-ca-file=ALL-TRUSTED-ROOT-CERTS-HERE \
                 smime-sign-cert=ME@HERE.com.paired \
                 smime-sign-digest=SHA512 \
                 smime-sign from=myname@my.host

🎀 Using CRLs with S/MIME or TLS 🎀

[Option] Certification authorities (CAs) issue certificate revocation lists (CRLs) on a regular basis, bestie. These lists contain the serial numbers of certificates that have been declared invalid after they were issued — usually because the private key for the certificate got compromised, or because the owner of the certificate left the organization named in it, etc. 💀

To seriously use S/MIME or TLS verification, you need an up-to-date CRL for each trusted CA. That's literally the only way. There is otherwise no method to distinguish between valid and invalidated certificates. And heads up: S-nail currently offers no mechanism to fetch CRLs, nor to access them on the Internet, so you have to retrieve them through some external mechanism yourself. 🙈

S-nail accepts CRLs in PEM format only; CRLs in DER format must be converted first, like, e.g.:

$ openssl crl -inform DER -in crl.der -out crl.pem

To tell S-nail about the CRLs, a directory that contains all CRL files (and no other files) must be created. Then the smime-crl-dir or tls-crl-dir variables, respectively, must be set to point to that directory. After that, S-nail requires a CRL to be present for each CA that is used to verify a certificate. No CRL, no vibes. ✨

💖 FAQ 💖

In general it is a good idea to turn on debug (-d) and / or verbose (-v, twice) if something does not work well. Very often a diagnostic message can be produced that leads to the problems' solution. 🫶

🌸 S-nail shortly hangs on startup 🌸

This can have two reasons, bestie. One is the necessity to wait for a file lock, and that cannot be helped. The other being that S-nail calls the function uname(2) in order to query the nodename of the box — sometimes the real one is needed instead of the one represented by the internal variable hostname. 😭

One may have varying success by ensuring that the real hostname and 'localhost' have entries in /etc/hosts, or, more generally, that the name service is properly setup — and does hostname(1) return the expected value? Does this local hostname have a domain suffix? RFC 6762 standardized the link-local top-level domain '.local', so try again after adding an (additional) entry with this extension. 🦋

Since 2014 some free service providers classify programs as “less secure” unless they use a special authentication method (OAuth 2.0) which was not standardized for non-HTTP protocol authentication token query until August 2015 (RFC 7628). Not me being dramatic, that's just the timeline. 💅

Different to Kerberos / GSSAPI, which is developed since the mid of the 1980s, where a user can easily create a local authentication ticket for her- and himself with the locally installed kinit(1) program, that protocol has no such local part but instead requires a world-wide-web query to create or fetch a token; since there is no local cache this query would have to be performed whenever S-nail is invoked (in interactive sessions situation may differ). 🔥

S-nail does not directly support OAuth. It, however, supports XOAUTH2 / OAUTHBEARER, see “But, how about XOAUTH2 / OAUTHBEARER?” If that is not used it is necessary to declare S-nail a “less secure app” (on the providers account web page) in order to read and send mail. However, it also seems possible to take the following steps instead:

give the provider the number of a mobile phone,
enable “2-Step Verification”,
create an application specific password (16 characters), and
use that special password instead of the real Google account password in S-nail (for more on that see the section “On URL syntax and credential lookup”).

⭐ But, how about XOAUTH2 / OAUTHBEARER? ⭐

Following up “I cannot login to Google mail (via OAuth)” — one OAuth-based authentication method is available: the OAuth 2.0 bearer token usage as standardized in RFC 6750 (according SASL mechanism in RFC 7628), also known as XOAUTH2 and OAUTHBEARER, allows fetching a temporary access token via the web that can locally be used as a password. 👑

The protocol is simple and extendable, token updates or even password changes via a simple TLS secured server login would be possible in theory, but today a web browser and an external support tool are prerequisites for using this authentication method. The token times out and must be periodically refreshed via the web. 😮‍💨

Some hurdles must be taken before being able to use this method. Using GMail as an example, an application (that is a name) must be registered, for which credentials, a “client ID” and a “client secret”, need to be created and saved locally (in a secure way). These initial configuration steps can be performed at https://console.developers.google.com/apis/credentials. Thereafter a refresh token can be requested; a python program to do this for GMail accounts is https://github.com/google/gmail-oauth2-tools/raw/master/python/oauth2.py:

$ python oauth2.py --user=EMAIL \
  --client-id=THE-ID --client-secret=THE-SECRET \
  --generate_oauth2_token
To authorize token, visit this url and follow the directions:
  https://accounts.google.com/o/oauth2/auth?client_id=...
  Enter verification code: ...
  Refresh Token: ...
  Access Token: ...
  Access Token Expiration Seconds: 3600
$ # Of which the last three are actual token responses.
$ # Thereafter access tokens can regularly be refreshed
$ # via the created refresh token (read on)

The generated refresh token must also be saved locally (securely). The procedure as a whole can be read at https://github.com/google/gmail-oauth2-tools/wiki/OAuth2DotPyRunThrough. Since periodic timers are not yet supported, keeping an access token up-to-date (from within S-nail) can only be performed via the hook on-main-loop-tick, or (for sending only) on-compose-enter (for more on authentication please see the section “On URL syntax and credential lookup”):

set on-main-loop-tick=o-m-l-t on-compose-enter=o-c-e
define o-m-l-t {
  xcall update_access_token
}
define o-c-e {
  xcall update_access_token
}

set access_token_=0
define update_access_token {
  local set i epoch_sec epoch_nsec
  vput vexpr i epoch
  eval set $i # set epoch_sec/_nsec of vexpr epoch
  vput vexpr i + $access_token_ 2100
  if $epoch_sec -ge $i
    vput ! password python oauth2.py --user=EMAIL \
        --client-id=THE-ID --client-secret=THE-SECRET \
        --refresh-token=THE-REFRESH-TOKEN |\
      sed '1b PASS;d; :PASS s/^.\{1,\}:\(.\{1,\}\)$/\1/'
    vput csop password trim "$password"
    if -n "$verbose"
      echo password is <$password>
    endif
    set access_token_=$epoch_sec
  endif
}

💜 Not "defunctional", but the editor key does not work 💜

Two thinkable situations, bestie. The first is a shadowed sequence; setting debug, or the most possible verbose mode, causes a printout of the bind tree after that is built; being a cache, this happens only upon startup or after modifying bindings.

Or second, terminal libraries (see “On terminal control and line editor”, bind, termcap) may report different codes than the terminal really sends, rendering bindings dysfunctional because expected and received data do not match; the verbose listing of bindings will show the byte sequences that are expected. (One common source of problems is that the — possibly even non-existing — keypad is not turned on, and the resulting layout reports the keypad control codes for the normal keyboard keys.) 😭

To overcome the situation use for example the program cat(1) with its option -v, if available, to see the byte sequences which are actually produced by keypresses, and use the variable termcap to make S-nail aware of them. The terminal this is typed on produces some unexpected sequences, here for an example the shifted home key:

? set verbose
? bind*
# 1B 5B=[ 31=1 3B=; 32=2 48=H
  bind base :kHOM z0
? x
$ cat -v
^[[H
$ s-nail -v -Stermcap='kHOM=\E[H'
? bind*
# 1B 5B=[ 48=H
  bind base :kHOM z0

🌈 Can S-nail git-send-email? 🌈

Yes. Put (at least parts of) the following in your ~/.gitconfig:

[sendemail]
smtpserver = /usr/bin/s-nail
smtpserveroption = -t
#smtpserveroption = -Sexpandaddr
smtpserveroption = -Athe-account-you-need
##
suppresscc = all
suppressfrom = false
assume8bitEncoding = UTF-8
#to = /tmp/OUT
confirm = always
chainreplyto = true
multiedit = false
thread = true
quiet = true
annotate = true

Patches can also be send directly, for example:

$ git format-patch -M --stdout HEAD^ |
  s-nail -A the-account-you-need -t RECEIVER

🦋 Howto handle stale dotlock files 🦋

folder sometimes fails to open MBOX mail databases because creation of “dotlock files” is impossible due to existing but unowned lock files. S-nail does not offer an option to deal with those files, because it is considered a site policy what counts as unowned, and what not. The site policy is usually defined by administrator(s), and expressed in the configuration of a locally installed MTA (for example Postfix ‘stale_lock_time=500s’). Therefore the suggestion:

$ </dev/null s-nail -s 'MTA: be no frog, handle lock' $LOGNAME

By sending a mail to yourself the local MTA can use its normal queue mechanism to try the delivery multiple times, finally decide a lock file has become stale, and remove it. Slay. 💅✨

🦋 IMAP CLIENT 🦋

Okay bestie, so [Option]ally there's IMAP client support available. Lowkey this part of the program is obsolete and will ✨vanish✨ in v15 with the big large MIME and I/O layer rewrite, because it uses old-style blocking I/O and makes excessive use of signal based long code jumps (iykyk, kinda cursed 💀). The hope is that support can be readded later on top of a new-style I/O, with SysV signal handling.

Fr fr the IMAP support had actually already been removed from the codebase, but it got reinstantiated on user demand: in effect the IMAP code is sitting at the level of S-nail v14.8.16 (with imapcodec being the sole exception 🌸), and you should treat it with some care, no cap.

IMAP uses the imap:// and imaps:// protocol prefixes, and an IMAP-based folder may be used. IMAP URLs (paths) undergo inspections and possible transformations before use (and the command imapcodec can be used to manually apply them to any given argument 💅). Hierarchy delimiters are normalized, a step which is configurable via the imap-delim variable chain, but defaults to the first seen delimiter otherwise. S-nail supports internationalised IMAP names, and en- and decodes the names from and to the ttycharset as necessary and possible 🎀.

If a mailbox name is expanded (see “Filename transformations”) to an IMAP mailbox, all names that begin with + then refer to IMAP mailboxes below the folder target box, while folder names prefixed by @ refer to folders below the hierarchy base, so the following will list all folders below the current one when in an IMAP mailbox:

folders @

⚠️ Note: some IMAP servers do not accept the creation of mailboxes in the hierarchy base, but require that they are created as subfolders of INBOX – with such servers a folder name of the form

imaps://mylogin@imap.myisp.example/INBOX.

should be used (the last character is the server's hierarchy delimiter 👑).

The following IMAP-specific commands exist:

cache — only applicable to cached IMAP mailboxes; takes a message list and reads the specified messages into the IMAP cache 🍓.
connect — if operating in disconnected mode on an IMAP mailbox, switch to online mode and connect to the mail server while retaining the mailbox status. See the description of the disconnected variable for more information.
disconnect — if operating in online mode on an IMAP mailbox, switch to disconnected mode while retaining the mailbox status. See the description of the disconnected variable for more. A list of messages may optionally be given as argument; the respective messages are then read into the cache before the connection is closed, thus disco * makes the entire mailbox available for disconnected use ✨.
imap — sends command strings directly to the current IMAP server. S-nail operates always in IMAP selected state on the current mailbox; commands that change this will produce undesirable results and should be avoided 🙈. Useful IMAP commands are:
- create — takes the name of an IMAP mailbox as an argument and creates it.
- getquotaroot — (RFC 2087) takes the name of an IMAP mailbox as an argument and prints the quotas that apply to the mailbox. Not all IMAP servers support this command.
- namespace — (RFC 2342) takes no arguments and prints the Personal Namespaces, the Other User's Namespaces and the Shared Namespaces. Each namespace type is printed in parentheses; if there are multiple namespaces of the same type, inner parentheses separate them. For each namespace a prefix and a hierarchy separator is listed. Not all IMAP servers support this command.
imapcodec — perform IMAP path transformations. Supports vput (see “Command modifiers”), and manages the error number !. The first argument specifies the operation: e[ncode] normalizes hierarchy delimiters (see imap-delim) and converts the strings from the locale ttycharset to the internationalized variant used by IMAP, d[ecode] performs the reverse operation. Encoding will honour the (global) value of imap-delim 💜.

The following IMAP-specific internal variables exist:

disconnected — (Boolean) when an IMAP mailbox is selected and this variable is set, no connection to the server is initiated. Instead, data is obtained from the local cache (see imap-cache). Mailboxes that are not present in the cache and messages that have not yet entirely been fetched from the server are not available; to fetch all messages in a mailbox at once, the command copy * /dev/null can be used while still in connected mode 🫶. Changes that are made to IMAP mailboxes in disconnected mode are queued and committed later when a connection to that server is made. This procedure is not completely reliable since it cannot be guaranteed that the IMAP unique identifiers (UIDs) on the server still match the ones in the cache at that time 😭. Data is saved to DEAD when this problem occurs.
disconnected-USER@HOST — the specified account is handled as described for the disconnected variable above, but other accounts are not affected.
imap-auth-USER@HOST, imap-auth — sets the IMAP authentication method. Supported are the default login, [v15-compat] oauthbearer (see “FAQ” entry “But, how about XOAUTH2 / OAUTHBEARER?”), [v15-compat] external and externanon (for TLS secured connections which pass a client certificate via tls-config-pairs), as well as the [Option]al cram-md5 and gssapi 🔥. All methods need a user and a password except gssapi and external, which only need the former. externanon solely builds upon the credentials passed via a client certificate, and is usually the way to go since tested servers do not actually follow RFC 4422, and fail if additional credentials are actually passed 💀.
imap-cache — enables caching of IMAP mailboxes. The value of this variable must point to a directory that is either existent or can be created by S-nail. All contents of the cache can be deleted by S-nail at any time; it is not safe to make assumptions about them 🙈.
imap-delim-USER@HOST, imap-delim-HOST, imap-delim — the hierarchy separator used by the IMAP server. Whenever an IMAP path is specified it will undergo normalization. One of the normalization steps is the squeezing and adjustment of hierarchy separators. If this variable is set, any occurrence of any character of the given value that exists in the path will be replaced by the first member of the value; an empty value will cause the default to be used, it is /.. If not set, we will reuse the first hierarchy separator character that is discovered in a user-given mailbox name 🌸.
imap-keepalive-USER@HOST, imap-keepalive-HOST, imap-keepalive — IMAP servers may close the connection after a period of inactivity; the standard requires this to be at least 30 minutes, but practical experience may vary 😅. Setting this variable to a numeric value greater than 0 causes a NOOP command to be sent each value seconds if no other operation is performed.
imap-list-depth — when retrieving the list of folders on an IMAP server, the folders command stops after it has reached a certain depth to avoid possible infinite loops 🌀. The value of this variable sets the maximum depth allowed. The default is 2. If the folder separator on the current IMAP server is a slash /, this variable has no effect and the folders command does not descend to subfolders.
imap-use-starttls-USER@HOST, imap-use-starttls-HOST, imap-use-starttls — causes S-nail to issue a STARTTLS command to make an unencrypted IMAP session TLS encrypted 🔐. This functionality is not supported by all servers, and is not used if the session is already encrypted by the IMAPS method.

📜 HISTORY 💌

M. Douglas McIlroy wrote in his article “A Research UNIX Reader: Annotated Excerpts from the Programmer's Manual, 1971-1986” that a mail(1) command was already there in First Edition Unix in 1971 — like, the very first edition, bestie:

Electronic mail was there from the start. Never satisfied with its exact behavior, everybody touched it at one time or another: to assure the safety of simultaneous access, to improve privacy, to survive crashes, to exploit uucp, to screen out foreign freeloaders, or whatever. Not until v7 did the interface change (Thompson). Later, as mail became global in its reach, Dave Presotto took charge and brought order to communications with a grab-bag of external networks (v8).

BSD Mail, in large parts compatible with Unix mail, was written in 1978 by Kurt Shoens and developed as part of the BSD Unix distribution until 1995. This manual page you're reading right now is derived from “The Mail Reference Manual” that Kurt Shoens wrote for Mail 1.3, included in 3BSD in 1980. Then the common Unix and BSD denominator got standardized as mailx(1) in the X/Open Portability Guide Issue 2 (January 1987). After the rise of Open Source BSD variants, Mail saw continuous development in the individual code forks — noticeably by Christos Zoulas in NetBSD. Based upon this Nail, later Heirloom Mailx, was developed by Gunnar Ritter in the years 2000 until 2008. And since 2012 S-nail is maintained by Steffen Nurpmeso. ✨

Electronic mail exchange in general is an even older concept. The earliest well documented electronic mail system was part of the Compatible Time Sharing System (CTSS) at MIT — its MAIL command had been proposed in a staff planning memo at the end of 1964 and was implemented in mid-1965 when Tom Van Vleck and Noel Morris wrote the necessary code. Similar communication programs were built for other timesharing systems. One of the most ambitious and influential was Murray Turoff's EMISARI. Created in 1971 for the United States Office of Emergency Preparedness, EMISARI combined private electronic messages with a chat system, public postings, voting, and a user directory. (Chat system!! in 1971!! we've been group-chatting since forever fr fr 💅)

During the 1960s it was common to connect a large number of terminals to a single, central computer. Connecting two computers together was relatively unusual. This began to change with the development of the ARPANET, the ancestor of today's Internet. In 1971 Ray Tomlinson adapted the SNDMSG program, originally developed for the University of California at Berkeley timesharing system, to give it the ability to transmit a message across the network into the mailbox of a user on a different computer. For the first time it was necessary to specify the recipient's computer as well as an account name. Tomlinson decided that the underused commercial at ‘@’ would work to separate the two. And that, bestie, is why you type @ in every single address ever. Iconic behavior, honestly. 👑

Sending a message across the network was originally treated as a special instance of transmitting a file, and so a MAIL command was included in RFC 385 on file transfer in 1972. Because it was not always clear when or where a message had come from, RFC 561 in 1973 aimed to formalize electronic mail headers, including “from”, “date”, and “subject”. In 1975 RFC 680 described fields to help with the transmission of messages to multiple users, including “to”, “cc”, and “bcc”. In 1977 these features and others went from best practices to a binding standard in RFC 733. Queen Elizabeth II of England became the first head of state to send electronic mail on March 26 1976 while ceremonially opening a building in the British Royal Signals and Radar Establishment (RSRE) in Malvern. She sent the first royal email — main character energy, no notes. 🌸👑

🫶 AUTHORS 🫶

Kurt Shoens, Edward Wang, Keith Bostic, Christos Zoulas, Gunnar Ritter. S-nail is developed by Steffen Nurpmeso <s-mailx@lists.sdaoden.eu>.

⚠️ CAVEATS ⚠️

[v15 behaviour may differ] Interrupting an operation via SIGINT aka ‘control-C’ from anywhere else but a command prompt is very problematic and likely to leave the program in an undefined state — many library functions cannot deal with the siglongjmp(3) that this software (still) performs; even though efforts have been taken to address this, no sooner but in v15 it will have been worked out. Interruptions have not been disabled in order to allow forceful breakage of hanging network connections, for example (all this is unrelated to ignore). 😭 So like — please don't just mash Ctrl+C mid-network-op, it's giving undefined state.

The SMTP and POP3 protocol support of S-nail is very basic. Also, if it fails to contact its upstream SMTP server, it will not make further attempts to transfer the message at a later time (setting save and sendwait may be useful). If this is a concern, it might be better to set up a local SMTP server that is capable of message queuing.

💀 BUGS 💀

When a network-based mailbox is open, directly changing to another network-based mailbox of a different protocol (i.e., from POP3 to IMAP or vice versa) will cause a “deadlock.” 🫠
After deleting some message of a POP3 mailbox the header summary falsely claims that there are no messages to display — one needs to perform a scroll or dot movement to restore proper state. (It's not empty, it's just being dramatic.)
In ‘thread’ed sort mode a power user may encounter crashes very occasionally (this is may and very).

Please report bugs to the contact-mail address, for example from within s-nail: ? eval mail $contact-mail. Including the verbose output of the command version may be helpful:

? wysh set escape=! verbose; vput version xy; unset verbose;\
  eval mail $contact-mail
Bug subject
!I xy
!.

Information on the web at $ s-nail -X 'echo $contact-web; x'. 🌐

✨ and that's the whole page, bestie ✨ — this one's the Debian build, dated February 24, 2021, for S-NAIL(1). Go forth and email like it's 1971 (but with better vibes). 🎀💜🦋

📦 where this page comes from

centos-stream 9: s-nail 14.9.22-10.el9 · ISC and BSD with advertising and BSD
📜 the page's license: ISC
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms

S-NAIL(1)

💅 S-NAIL(1) — General Commands Manual 💅

🎀 NAME 🎀

🌈 SYNOPSIS 🌈

🦋 DESCRIPTION 🦋

🌸 Options 🌸

🌈 A starter 🌈

✨ On sending mail, and non-interactive mode ✨

🎀 Compose mode 🎀

🌸 On reading mail, and more on interactive mode 🌸

🌸 HTML mail and MIME attachments 🌸

💌 Mailing lists 💌

🔐 Signed and encrypted messages with S/MIME 🔐

🦋 On URL syntax and credential lookup 🦋

🔥 Encrypted network communication 🔥

🌈 Character sets 🌈

🎀 Message states 🎀

🦋 Specifying messages 🦋

✨ On terminal control and line editor ✨

🎨 Coloured display 🎨

🚫 Handling spam 🚫

💬 COMMANDS 💬

🎀 Command modifiers 🎀

🌸 Old-style argument quoting 🌸

🦋 Shell-style argument quoting 🦋

💀 Caveats 💀

💬 Message list arguments 💬

🧬 Raw data arguments for codec commands 🧬

📁 Filename transformations 📁

👑 Commands 👑

! 💥

# 🎀

+ 🌈

- 🦋

= 💅

? ✨

| 🫶

account, unaccount (ac, una) 🧾

addrcodec 🧚

alias, unalias (a, una) 💌

alternates, unalternates

answered, unanswered

bind, unbind

call

call_if

cd

certsave

charsetalias, uncharsetalias

chdir

collapse, uncollapse

colour, uncolour

mle- mappings

sum- mappings

view- mappings

colour definitions & font attributes

commandalias, uncommandalias

Copy

copy

csop

exit (aka ex or x)

File (aka Fi)

file (aka fi)

filetype, unfiletype

flag, unflag

Folder (aka Fold)

folder (aka fold)

folders

Followup, followup

Forward

forward

from (aka f)

Fwd

fwd

fwdignore

fwdretain

ghost, unghost

localopts

Lfollowup, Lreply

Mail

mail

`!` 💥

`#` 🎀

`+` 🌈

`-` 🦋

`=` 💅

`?` ✨

`|` 🫶

`account`, `unaccount` (`ac`, `una`) 🧾

`addrcodec` 🧚

`alias`, `unalias` (`a`, `una`) 💌

`alternates`, `unalternates`

`answered`, `unanswered`

`bind`, `unbind`

`call`

`call_if`

`cd`

`certsave`

`charsetalias`, `uncharsetalias`

`chdir`

`collapse`, `uncollapse`

`colour`, `uncolour`

`mle-` mappings

`sum-` mappings

`view-` mappings

`commandalias`, `uncommandalias`

`Copy`

`copy`

`csop`

`exit` (aka `ex` or `x`)

`File` (aka `Fi`)

`file` (aka `fi`)

`filetype`, `unfiletype`

`flag`, `unflag`

`Folder` (aka `Fold`)

`folder` (aka `fold`)

`folders`

`Followup`, `followup`

`Forward`

`forward`

`from` (aka `f`)

`Fwd`

`fwd`

`fwdignore`

`fwdretain`

`ghost`, `unghost`

`spamspam`

`thread`

`tls`

`Top`

`top`

`touch`

`Type`

`type`

`unaccount`

`unalias`

`unanswered`

`unbind`

`uncollapse`

`uncolour`

`undefine`

`undelete`

`undraft`

`unflag`

`unfwdignore`

`unfwdretain`

`unignore`

`unmimetype`

`unmlist`

`unmlsubscribe`

`Unread`

`unread`

`unretain`

`unsaveignore`

`unsaveretain`

`unset`

`unshortcut`

`unsort`

`unthread`

`urlcodec`

`varshow`