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

       mailaddr - mail addressing description

       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 examples:


       (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.


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

       IETF RFC 5322 ⟨
       This page is part of release 5.11 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)