aliases(5) — Linux manual page


ALIASES(5)                 File Formats Manual                ALIASES(5)

NAME         top

       aliases — aliases file for smtpd

DESCRIPTION         top

       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

       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

               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.

FILES         top

       /etc/mail/aliases     Default aliases file.

SEE ALSO         top

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

HISTORY         top

       The aliases file format appeared in 4.0BSD.

COLOPHON         top

       This page is part of the OpenSMTPD (a FREE implementation of the
       server-side SMTP protocol) project.  Information about the
       project can be found at  If you have
       a bug report for this manual page, see
       ⟨⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ on 2024-06-14.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2024-06-09.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

GNU                         February 13, 2021                 ALIASES(5)

Pages that refer to this page: setaliasent(3)mailaddr(7)