ALIASES(5)                  BSD File Formats Manual                 ALIASES(5)

     aliases — aliases file for smtpd

     This manual page describes the format of the aliases file, as used by
     smtpd(8).  An alias in its simplest form is used to assign an arbitrary
     name to an email address, or a group of email addresses.  This provides a
     convenient way to send mail.  For example an alias could refer to all
     users of a group: email to that alias would be sent to all members of the
     group.  Much more complex aliases can be defined however: an alias can
     refer to other aliases, be used to send mail to a file instead of another
     person, or to execute various commands.

     Within the file, ‘#’ is a comment delimiter; anything placed after it is
     discarded.  The file consists of key/value mappings of the form:

           key: value1, value2, value3, ...

     key is always folded to lowercase before alias lookups to ensure that
     there can be no ambiguity.  The key is expanded to the corresponding
     values, which consist of one or more of the following:

     user    A user on the host machine.  The user must have a valid entry in
             the passwd(5) database file.

             Append messages to file, specified by its absolute pathname.

             Pipe the message to command on its standard input.  The command
             is run under the privileges of the daemon's unprivileged account.

             Include any definitions in file as alias entries.  The format of
             the file is identical to this one.

             An email address in RFC 5322 format.  If an address extension is
             appended to the user-part, it is first compared for an exact
             match.  It is then stripped so that an address such as
    will only use the part that precedes ‘+’ as
             a key.

     error:code message
             A status code and message to return.  The code must be 3 digits,
             starting 4XX (TempFail) or 5XX (PermFail).  The message must be
             present and can be freely chosen.

     /etc/smtpd/aliases     Default aliases file.

     smtpd.conf(5), makemap(8), newaliases(8), smtpd(8)

     The aliases file format appeared in 4.0BSD.

BSD                             April 23, 2020                             BSD