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MAILADDR(7)            Miscellaneous Information Manual            MAILADDR(7)

NAME
     mailaddr - mail addressing description

DESCRIPTION
     Mail addresses are based on the Internet protocol listed at the end of
     this manual page.  These addresses are in the general format

           user@domain

     where a domain is a hierarchical dot separated list of subdomains.  For
     example, a valid address is:

           eric@CS.Berkeley.EDU

     Unlike some other (now obsolete) forms of addressing, domains do not
     imply any routing, or the existence of a particular host.  Simply because
     mail may be sent to ``user@somedomain.com'' does not imply that there is
     any actual host named ``somedomain.com'', and does not imply a particular
     routing of the message.  Routing is performed by Mail Transport Agents,
     such as postfix(1), based on policies set in the MTA's configuration.

   Abbreviation
     Under certain circumstances it may not be necessary to type the entire
     domain name.  In general, anything following the first dot may be omitted
     if it is the same as the domain from which you are sending the message.
     For example, a user on ``calder.berkeley.edu'' could send to ``eric@CS''
     without adding the ``berkeley.edu'' since it is the same on both sending
     and receiving hosts.  Whether abbreviation is permitted depends on how
     your site is configured.

   Case Distinctions
     Domain names (i.e., anything after the ``@'' sign) may be given in any
     mixture of upper and lower case.  Most hosts accept any combination of
     case in user names, although there are exceptions.

   Postmaster
     Every site is required to have a user or user alias designated
     ``postmaster'' to which problems with the mail system may be addressed,
     for example:

           postmaster@CS.Berkeley.EDU

   Obsolete Formats
     Certain old address formats, such as UUCP ``bang path'' addresses,
     explicitly routed internet addresses (so-called ``route-addrs'' and the
     ``percent hack'') and others have been used historically.  All these
     addressing formats are now considered obsolete, and should no longer be
     used.

     To some extent, MTAs attempt to provide backward compatibility for these
     addressing forms, but in practice many of them no longer work.  Users
     should always use standard Internet style addresses.

SEE ALSO
     mail(1)

     D. H. Crocker, Standard for the Format of Arpa Internet Text Messages,
     RFC, 822, August 1982.

HISTORY
     mailaddr appeared in 4.2BSD.

BUGS
     The RFC 822 group syntax (``group:user1,user2,user3;'') is not supported
     except in the special case of ``group:;'' because of a conflict with old
     berknet-style addresses, not that anyone cares about either berknet or
     group syntax style addresses any longer.

NetBSD 10.99                     June 16, 1998                    NetBSD 10.99