MH-MAIL(5mh)

💌 mh-mail — the vibe check on message format for the nmh message system 💌

okay bestie, gather round, because this is the page that explains what a message even is in nmh. this is MH-MAIL(5mh), and it's lowkey foundational. no cap.

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✨ NAME ✨

mh-mail — message format for nmh message system

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🌸 DESCRIPTION 🌸

so nmh processes messages in one particular format. and here's the tea: neither Bell nor Berkeley mailers produce message files in the format that nmh prefers, but nmh can read message files in that format anyway. so like, it's flexible. it ate. 💅

Every single user has a mail drop, and that mail drop initially receives all messages processed by post. then inc will read from that mail drop and incorporate new messages found there into the user's own mail folders (typically +inbox). the mail drop consists of one or more messages. iconic behaviour tbh.

Messages are expected to consist of lines of text. Graphics and binary data are not handled. No data compression is accepted. All text is clear ASCII 7-bit data. so like… no images, no zip files, no funky bytes. just text. periodt. 🎀

The general "memo" framework of RFC 822 is used. A message consists of a block of information in a rigid format, followed by general text with no specified format. the rigidly formatted first part of a message is called the header, and the free-format portion is called the body. the header must always exist, but the body is optional. these parts are separated by an empty line, i.e., two consecutive newline characters.

within nmh, the header and body may be separated by a line consisting of dashes. noted. 🫶

here's what that looks like:

From: Local Mailbox <user@example.com>
To:
cc:
Fcc: +outbox
Subject:

The header is composed of one or more header items. Each header item can be viewed as a single logical line of ASCII characters. If the text of a header item extends across several real lines, the continuation lines are indicated by leading spaces or tabs. (yes bestie, leading whitespace is load-bearing here, don't strip it.)

Each header item is called a component and is composed of a keyword or name, along with associated text. the keyword begins at the left margin, may not contain spaces or tabs, may not exceed 63 characters (as specified by RFC 822), and is terminated by a colon (:). Certain components (as identified by their keywords) must follow rigidly defined formats in their text portions.

The text for most formatted components (e.g., Date: and Message-Id:) is produced automatically. the only ones entered by the user are address fields such as To:, cc:, etc. Internet addresses are assigned mailbox names and host computer specifications. the rough format is local@domain, such as MH@UCI, or MH@UCI-ICSA.ARPA. Multiple addresses are separated by commas. A missing host/domain is assumed to be the local host/domain. (so if you're lazy about the domain, it just assumes local. generous king behaviour. 👑)

As mentioned above, a blank line (or a line of dashes) signals that all following text up to the end of the file is the body. No formatting is expected or enforced within the body. do whatever in there, it's your world.

Following is a list of header components that are considered meaningful to various nmh programs. buckle up, there's a lot, but they're all kinda important so we're not skipping a single one. 🧚

💖 Date:

Added by post, contains date and time of the message's entry into the mail transport system.

💖 From:

This header is filled in by default with the system's idea of the user's local mailbox. This can be changed with the Local-Mailbox profile entry. It contains the address of the author or authors (may be more than one if a Sender: field is present). For a standard reply (using repl), the reply address is constructed by checking the following headers (in this order): Mail-Reply-To:, Reply-To:, From:, Sender:.

🚨 A From: header MUST exist when the message is sent to post, otherwise the message will be rejected. no From:, no entry. that's the vibe check and you failed it, sorry babe. 😭

💖 Envelope-From:

Used by post to specify a value for the sender's envelope address to the mail transport system. If omitted, post will use the value of the Sender: or the From: header. See send(1) for more details.

💖 Mail-Reply-To:

For a standard reply (using repl), the reply address is constructed by checking the following headers (in this order): Mail-Reply-To:, Reply-To:, From:, Sender:.

💖 Mail-Followup-To:

When making a "group" reply (using repl -group), any addresses in this field will take precedence, and no other reply address will be added to the draft. If this header is not available, then the return addresses will be constructed from the Mail-Reply-To:, or Reply-To:, or From:, along with adding the addresses from the headers To:, cc:, as well as adding your personal address.

💖 Reply-To:

For a standard reply (using repl), the reply address is constructed by checking the following headers (in this order): Mail-Reply-To:, Reply-To:, From:, Sender:.

💖 Sender:

Required by post in the event that the message has multiple addresses on the From: line. It is otherwise optional. This line should contain the address of the actual sender.

💖 To:

Contains addresses of primary recipients. the mains. the VIPs. ✨

💖 cc:

Contains addresses of secondary recipients.

💖 Bcc:

Still more recipients. However, the Bcc: line is not copied onto the message as delivered, so these recipients are not listed. nmh uses an encapsulation method for blind copies, see send(1). sneaky but sanctioned. 🙈

💖 Dcc:

Still more recipients. However, the Dcc: line is not copied onto the messages as delivered. Recipients on the Dcc: line receive the same message as recipients on the To: and cc: lines. See send(1) for more details.

Dcc is not supported with the sendmail/pipe mail transport method. so if that's your transport, this one's just not gonna work, bestie. 💀

💖 Fcc:

Causes post to copy the message into the specified folder for the sender, if the message was successfully given to the transport system.

💖 Message-ID:

A unique message identifier added by post if the -msgid flag is set.

💖 Subject:

Sender's commentary. It is displayed by scan.

💖 In-Reply-To:

A commentary line added by repl when replying to a message.

💖 Resent-Date:

Added when redistributing a message by post.

💖 Resent-From:

Used instead of the From: header when post redistributes a message. See From:.

💖 Resent-To:

New recipients for a message resent by dist.

💖 Resent-cc:

Still more recipients. See cc: and Resent-To:.

💖 Resent-Bcc:

Even more recipients. See Bcc: and Resent-To:.

💖 Resent-Fcc:

Copy resent message into a folder. See Fcc: and Resent-To:.

💖 Resent-Message-Id:

A unique identifier glued on by post if the -msgid flag is set. See Message-Id: and Resent-To:.

💖 Resent:

Annotation for dist under the -annotate option.

💖 Forwarded:

Annotation for forw under the -annotate option.

💖 Replied:

Annotation for repl under the -annotate option.

💖 Attach:

Used by mhbuild to specify a filename to attach to this message. See mhbuild(1) for more information.

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📁 FILES 📁

• /var/mail/$USER — Location of mail drop.

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👀 SEE ALSO 👀

• Standard for the Format of ARPA Internet Text Messages (RFC 822)

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🦋 CONTEXT 🦋

None

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and that's the whole page, bestie!! you now officially know more about message format than like 90% of people who send email. slay. 💜

this whole thing came to you from nmh-1.8, dated 2014-01-08 — yeah she's a lil vintage but she's still absolutely eating, and honestly? timeless. mwah. 💅🎀✨