EXTSMAIL.EXTERNALS(5)

💖 EXTSMAIL.EXTERNALS 💖

okay so this is the extsmail.externals page, from the File Formats Manual section — it's a file formats situation, manual 5, iykyk. sit down bestie, we're configuring which external commands send your mail, robustly. ✨

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✨ NAME ✨

extsmail.externals — the config file where you tell things which external commands to robustly send e-mail via 🦋

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🌸 DESCRIPTION 🌸

So extsmail.externals is literally the file that configures extsmaild(1). 💅 It's made up of one or more group declarations. Each group is zero or more match / reject clauses, and then one or more external declarations. And an external is just one or more assignments of key = value pairs. that's it, that's the whole structure. 🎀

When it's actually sending messages, extsmaild(1) does this: first it searches through the externals file, in order, looking for a group whose match / reject clauses match the message in question. 👀 If a group doesn't have any of those clauses, it just automatically matches all messages — no cap, it's a yes-man. Match / reject clauses currently only match against headers, and they use standard POSiX extended regular expressions (peep re_format(7) for the deets). Then extsmaild(1) tries each external in the group, in order, to send the message successfully. slay. 💅

The grammar for this file is, fr fr, exactly this:

group    ::= { matches* external+ }

matches  ::= match
           | reject
match    ::= MATCH HEADER string
reject   ::= REJECT HEADER string

external ::= EXTERNAL ID { defn+ }

defn     ::= ID = STRING
           | ID = TIME

TIME     ::= [0-9]+[dhms]

Valid assignments within an external are these two cuties 👑:

• sendmail — defines the external shell command used to send e-mail. that's the one doing the actual work, main character energy fr.
• timeout — if extsmaild(1) is running in daemon mode, this value sets the length of time extsmaild(1) will retry this external before giving up and trying the next external in the group. 😭 Times are written as a number followed by d (days), h (hours), m (minutes), or s (seconds). But heads up bestie — if extsmaild(1) is running in batch mode, the timeout value is ignored. periodt.

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🎀 FILES 🎀

The extsmail configuration file is searched for, in order, in these locations:

• ~/.extsmail/externals — per-user configuration. 🫶 this one's yours, yours, yours.
• /etc/extsmail/externals — system-wide configuration. 👑

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🌈 EXAMPLES 🌈

The simplest externals file sending e-mail via ssh(1) looks like this, and honestly? iconic for how little it does:

group {
    external mymachine {
        sendmail = "/usr/bin/ssh -q -C -l user mymachine.net /usr/sbin/sendmail -t"
    }
}

where mymachine is a human-friendly name given to an external (it does not effect processing — it's purely a vibe, a nickname, a little label 💅), and user is the username on the remote machine mymachine.net. 🦋

A more complex example using multiple groups, message matching, and multiple external commands looks like this:

group {
    match header "^To:.*@foo.com"

    external foo {
        sendmail = "/usr/bin/ssh -q -C -l user shell.foo.com /usr/sbin/sendmail -t"
    }
}

group {
    external mymachine {
        sendmail = "/usr/bin/ssh -q -C -l user mymachine.net /usr/sbin/sendmail -t"
    }

    external bk {
        sendmail = "/usr/bin/ssh -q -C -l user bk.mymachine.net /usr/sbin/sendmail -t"
    }
}

see how the first group is picky and the second one is like "sure whatever, try both"? that's the energy. ✨

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👀 SEE ALSO 👀

extsmail(1), extsmail.conf(5), extsmaild(1)

go read those too bestie, they're the whole friend group 🫶

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💜 AUTHORS 💜

Laurence Tratt <http://tratt.net/laurie/> — thank you for your service, legend 👑

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and that's the whole page!! this one shipped as part of Debian, dated November 2, 2008 — yes, 2008, it's vintage, it's retro, it's still slaying 💅✨ mwah, go send some mail 🍓💖