sendmail, 4th Edition

The MAILER-DAEMON Alias

When mail is bounced, the notification of failure is always shown as being from the sender whose name is defined by the $n sendmail macro ($n on page 836). Traditionally, that macro is given the value mailer-daemon. The following, for example, shows how to use the confMAILER_NAME mc macro to assign the value mailer-daemon to the $n sendmail macro:

define(`confMAILER_NAME', `mailer-daemon')

That tradition is enforced by the fact that if $n is not defined, it defaults to mailer-daemon.

There needs to be an alias for whatever name is defined for $n because users occasionally make the mistake of replying to bounced mail. Two typical choices (one or the other) are:

mailer-daemon: postmaster
mailer-daemon: /dev/null

Here, the name to the left of the colon should be whatever was defined for $n in the configuration file, traditionally (and recommended to be) mailer-daemon. The first alias forwards all mailer-daemon reply mail to the postmaster. Many site administrators prefer the second, which discards such mail by using /dev/null.