mailaddr - mail addressing 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:
[email protected]
Unlike some other forms of addressing, domains do not imply
any routing.
Thus, although this address is specified as an Internet address, it might
travel by an alternate route if that were more convenient or
efficient.
For example, at Berkeley, the associated message would probably go directly
to CS over the Ethernet rather than going via the
Berkeley Internet
gateway.
Abbreviation [Toc] [Back]
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.
Compatibility [Toc] [Back]
Certain old address formats are converted to the new format
to provide
compatibility with the previous mail system. In particular,
user@host
and
[email protected]ain
are allowed;
host.domain!user
is converted to
[email protected]ain
and
host!user
is converted to
[email protected]
This is normally converted back to the ``host!user'' form
before being
sent on for compatibility with older UUCP hosts.
Case distinctions [Toc] [Back]
Domain names (i.e., anything after the ``@'' sign) may be
given in any
mixture of upper and lower case with the exception of UUCP
hostnames.
Most hosts accept any combination of case in user names,
with the notable
exception of MULTICS sites.
Route-addrs [Toc] [Back]
Under some circumstances it may be necessary to route a message through
several hosts to get it to the final destination. Normally
this routing
is done automatically, but sometimes it is desirable to
route the message
manually. 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''. This path is forced
even if
there is a more efficient path 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 sender.
[Note: The route-addr syntax is officially deprecated in RFC
1123 and
should not be used.]
Many sites also support the ``percent hack'' for simplistic
routing:
user%hostc%hostb@hosta
is routed as indicated in the previous example.
Postmaster [Toc] [Back]
Every site is required to have a user or user alias designated
``postmaster'' to which problems with the mail system may be
addressed.
Other networks [Toc] [Back]
Some other networks can be reached by giving the name of the
network as
the last component of the domain. This is not a standard
feature and may
not be supported at all sites. For example, messages to
CSNET or BITNET
sites can often be sent to ``[email protected]'' or ``[email protected]'',
respectively.
mail(1), sendmail(8)
Crocker, D. H., Standard for the Format of Arpa Internet
Text Messages,
RFC 822.
mailaddr appeared in 4.2 BSD.
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.
Route-Address syntax is grotty.
UUCP- and Internet-style addresses do not coexist politely.
OpenBSD 3.6 June 16, 1993
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