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mailaddr(7) Miscellaneous Information 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
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.
/etc/aliases
~/.forward
mail(1), aliases(5), forward(5), sendmail(8)
IETF RFC 5322 ⟨http://www.ietf.org/rfc/rfc5322.txt⟩
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
4.2 Berkeley Distribution 2025-05-17 mailaddr(7)
Pages that refer to this page: hostname(7), uri(7)
Copyright and license for this manual page
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