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 sub-
domains. For example, the addresses
Eric Allman <email@example.com>
firstname.lastname@example.org (Eric Allman)
are valid forms of the same address.
The domain part (``monet.berkeley.edu'') may be the name of
an internet host, or it may be a logical mail address. The
domain part is not case sensitive.
The local part (``eric'') is often a user name, but its
meaning is defined by the local software. It can be case
sensitive, but usually isn't. 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 inernal mail system that lacks proper internet
support, an UUCP gateway, and the last one is just boring
The real-name part (``Eric Allman'') can either be placed
first, outside <>, or last, inside (). (Strictly speaking
the two aren't the same, but the difference is outside the
scope of this page.) The name may have to be quoted using
"" if it contains certain characters, most commonly ``.'':
"Eric P. Allman" <email@example.com>
Many mail systems let users abbreviate the domain name. For
instance, users at berkeley.edu may get away with
``eric@monet'' to send mail to Eric Allman. This behavior is
Under some circumstances it may be necessary to route a mes-
sage through several hosts to get it to the final destina-
tion. Normally this happens automatically and invisibly,
but sometimes not, particularly with old and broken
software. 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. Some hosts
disregard route-addrs and send directly to hostc.
Route-addrs occur frequently on return addresses, since
these are generally augmented by the software at each host.
It is generally possible to ignore all but the
``user@hostc'' part of the address to determine the actual
Every site is required to have a user or user alias desig-
nated ``postmaster'' to which problems with the mail system
may be addressed. The ``postmaster'' address is not case
FREQUENTLY ASKED QUESTIONS
rtfm.mit.edu and many mirrors store a collection of FAQs.
Please find and use a nearby FAQ archive; there are dozens
or hundreds around the world. mail/inter-network-guide
explains how to send mail between many different networks.
mail/country-codes lists the top level domains (e.g. ``no''
is Norway and ``ea'' is Eritrea). mail/college-email/part*
gives some useful tips on how to locate e-mail addresses.
binmail(1), mail(1), mconnect(1), forward(5), aliases(5),
sendmail(8), vrfy(8), RFC822 (Standard for the Format of
Arpa Internet Text Messages).