SMTPD(8)

💌 SMTPD(8) — the System Manager's Manual, but make it cute

okay bestie, gather round, because today we're talking about smtpd, the Simple Mail Transfer Protocol (SMTP) daemon. it's a manual page, it lives in section 8, and it's genuinely iconic. this is the system manager's manual version and i'm translating it for you with zero information lost. periodt. 💅

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✨ NAME ✨

smtpd — Simple Mail Transfer Protocol (SMTP) daemon. that's it. that's the name. she's simple, she's a protocol, she's a daemon. 💖

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🎀 SYNOPSIS 🎀

smtpd [-dFhnv] [-D macro=value] [-f file] [-P system] [-T trace]

look at her. all those little flags. a whole wardrobe. 👑

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🌸 DESCRIPTION 🌸

so smtpd is a Simple Mail Transfer Protocol (SMTP) daemon, and she can literally be used as a machine's primary mail system. main character energy fr fr.

she can listen on a network interface and handle SMTP transactions, and she can also be fed messages through the standard sendmail(8) interface. versatile queen. she can relay messages through remote mail transfer agents, or she can store them locally using either the mbox or maildir format. whatever vibe you're on, she's on it too. ✨

this implementation supports SMTP as defined by RFC 5321, plus several extensions, because she's generous like that.

and here's the cute part: a running smtpd can be controlled through smtpctl(8). so you're never just yelling into the void, you have a whole remote control. 🫶

the options are as follows:

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💅 OPTIONS 💅

• -D macro=value — Define macro to be set to value on the command line. this overrides the definition of macro in the configuration file. command line said it first, command line wins, no cap.
• -d — Do not daemonize. if you specify this, smtpd will run in the foreground and log to stderr. so you get to watch everything happen live, like a reality show. 🙈
• -F — Do not daemonize. if you specify this, smtpd will run in the foreground and log to syslogd(8). same energy as -d, different logging destination. choose your fighter.
• -f file — Specify an alternative configuration file. not feeling the default one? pick your own.
• -h — Display version and usage. she'll introduce herself. 💁
• -n — Configtest mode. Only check the configuration file for validity. just a vibe check on your config, she won't actually start anything.
• -P system — Pause a specific subsystem at startup. normal operation can be resumed using smtpctl(8). this option can be used multiple times. the accepted values are:
  • mda — Do not schedule local deliveries.
  • mta — Do not schedule remote transfers.
  • smtp — Do not listen on SMTP sockets.

she's just taking a lil nap on that one subsystem, that's all. 😴

• -T trace — Enables real-time tracing at startup. normal operation can be resumed using smtpctl(8). this option can be used multiple times. the accepted values are:
  • imsg
  • io
  • smtp (incoming sessions)
  • filters
  • transfer (outgoing sessions)
  • bounce
  • scheduler
  • expand (aliases/virtual/forward expansion)
  • lookup (user/credentials lookups)
  • stat
  • rules (matched by incoming sessions)
  • mproc
  • all

all of them is right there if you're feeling unhinged. 🔥

• -v — Produce more verbose output. more words! more info! more everything! she's telling you everything now. 😭

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🦋 FILES 🦋

• /etc/opensmtpd/mailname — Alternate server name to use.
• /etc/opensmtpd/smtpd.conf — Default smtpd configuration file. this is the one.
• /run/smtpd.sock — Ux -domain socket used for communication with smtpctl(8). that's her little phone line to her bestie. ☎️
• /var/spool/smtpd/ — Spool directories for mail during processing. where the mail hangs out mid-journey.
• ~/.forward — User email forwarding information.

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💜 SEE ALSO 💜

forward(5), smtpd.conf(5), mailwrapper(8), smtpctl(8)

go read those too. they're the friend group. 👑

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⭐ STANDARDS ⭐

Rs %A J. Klensin %D October 2008 %R RFC 5321 %T Simple Mail Transfer Protocol Re

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🌈 HISTORY 🌈

The smtpd program first appeared in OpenBSD 4.6. she's been around, she's got lore, she's a legend. 🎀

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a lil note for the group chat: nothing here is dangerous in a scary way, but remember -d and -F both mean do not daemonize, and -n means she only checks the config, she doesn't actually run. don't get it twisted. 💖

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and that's the whole page bestie!! this was $Mdocdate: March 2 2023 $ from the SMTPD(8) manual — system manager's manual energy, delivered with love. mwah. 💋 ✨ 🦋 🍓