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mailaddr(7)                       Miscellaneous Information Manual                       mailaddr(7)

NAME
       mailaddr - mail addressing description

DESCRIPTION
       This  manual page gives a brief introduction to SMTP mail addresses, as used on the Internet.
       These addresses are in the general format

           user@domain

       where a domain is a hierarchical dot-separated list of subdomains.  These examples are  valid
       forms of the same address:

           john.doe AT monet.com
           John Doe <john.doe AT monet.com>
           john.doe AT monet.com (John Doe)

       The  domain  part  ("monet.example.com") is a mail-accepting domain.  It can be a host and in
       the past it usually was, but it doesn't have to be.  The domain part is not case sensitive.

       The local part ("john.doe") is often a username, but its meaning  is  defined  by  the  local
       software.  Sometimes it is case sensitive, although that is unusual.  If you see a local-part
       that looks like garbage, it is usually because of a gateway between an internal e-mail system
       and the net, here are some examples:

           "surname/admd=telemail/c=us/o=hp/prmd=hp"@some.where
           USER%SOMETHING AT some.where
           machine!machine!name AT some.where
           I2461572 AT some.where

       (These  are,  respectively,  an X.400 gateway, a gateway to an arbitrary internal mail system
       that lacks proper internet support, an UUCP gateway, and the last one is just boring username
       policy.)

       The real-name part ("John Doe") can either be  placed  before  <>,  or  in  ()  at  the  end.
       (Strictly  speaking  the  two aren't the same, but the difference is beyond the scope of this
       page.)  The name may have to be quoted using "", for example, if it contains ".":

           "John Q. Doe" <john.doe AT monet.com>

   Abbreviation
       Some mail systems let users abbreviate the domain name.  For instance, users  at  example.com
       may  get  away  with "john.doe@monet" to send mail to John Doe.  This behavior is deprecated.
       Sometimes it works, but you should not depend on it.

   Route-addrs
       In the past, sometimes one had to route a message through several hosts  to  get  it  to  its
       final  destination.   Addresses  which show these relays are termed "route-addrs".  These use
       the syntax:

           <@hosta,@hostb:user@hostc>

       This specifies that the message should be sent to hosta, from there to hostb, and finally  to
       hostc.  Many hosts disregard route-addrs and send directly to hostc.

       Route-addrs  are  very  unusual  now.   They  occur  sometimes  in  old mail archives.  It is
       generally possible to ignore all but the "user@hostc" part of the address  to  determine  the
       actual address.

   Postmaster
       Every site is required to have a user or user alias designated "postmaster" to which problems
       with the mail system may be addressed.  The "postmaster" address is not case sensitive.

FILES
       /etc/aliases
       ~/.forward

SEE ALSO
       mail(1), aliases(5), forward(5), sendmail(8)

       IETF RFC 5322

4.2 Berkeley Distribution                    2023-10-31                                  mailaddr(7)