SMTPD(8) System Manager's Manual SMTPD(8)

smtpd — Simple Mail Transfer Protocol (SMTP) daemon

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

smtpd is a Simple Mail Transfer Protocol (SMTP) daemon which can be used as a machine's primary mail system. smtpd can listen on a network interface and handle SMTP transactions; it can also be fed messages through the standard sendmail(8) interface. It can relay messages through remote mail transfer agents or store them locally using either the mbox or maildir format. This implementation supports SMTP as defined by RFC 5321 as well as several extensions. A running smtpd can be controlled through smtpctl(8).

The options are as follows:

macro=value
Define macro to be set to value on the command line. Overrides the definition of macro in the configuration file.
Do not daemonize. If this option is specified, smtpd will run in the foreground and log to .
Do not daemonize. If this option is specified, smtpd will run in the foreground and log to syslogd(8).
file
Specify an alternative configuration file.
Display version and usage.
Configtest mode. Only check the configuration file for validity.
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.
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
Produce more verbose output.

/etc/mailname
Alternate server name to use.
/etc/smtpd.conf
Default smtpd configuration file.
/var/run/smtpd.sock
UNIX-domain socket used for communication with smtpctl(8).
/var/spool/smtpd/
Spool directories for mail during processing.
~/.forward
User email forwarding information.

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

J. Klensin, Simple Mail Transfer Protocol, RFC 5321, October 2008.

The smtpd program first appeared in OpenBSD 4.6.

March 2, 2023 Debian