mailaddr(7) — Linux manual page


MAILADDR(7)                Linux User's Manual               MAILADDR(7)

NAME         top

       mailaddr - mail addressing description

DESCRIPTION         top

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


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

            John Doe <>
   (John Doe)

       The domain part ("") 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


       (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" <>

       Some mail systems let users abbreviate the domain name.  For
       instance, users at 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.

       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:


       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.

       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         top


SEE ALSO         top

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

       IETF RFC 5322 ⟨

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

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

Pages that refer to this page: hostname(7)uri(7)