MAILADDR(7)                                                                Linux User's 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@monet.example.com
            John Doe <john.doe@monet.example.com>
            john.doe@monet.example.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@some.where
            machine!machine!name@some.where
            I2461572@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@monet.example.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 ⟨http://www.ietf.org/rfc/rfc5322.txt⟩

4.2 Berkeley Distribution                                                      2020-08-13                                                                    MAILADDR(7)