MAILADDR(7) FreeBSD Miscellaneous Information Manual MAILADDR(7)
NAME
mailaddr - mail addressing description
DESCRIPTION
Mail addresses are based on the ARPANET 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, the address
[email protected]
is normally interpreted from right to left: the message should go to the
ARPA name tables (which do not correspond exactly to the physical
ARPANET), then to the Berkeley gateway, after which it should go to the
local host monet. When the message reaches monet it is delivered to the
user ``eric''.
Unlike some other forms of addressing, this does not imply any routing.
Thus, although this address is specified as an ARPA 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 monet over the Ethernet rather than going via the Berkeley
ARPANET gateway.
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@monet'' without adding the ``berkeley.edu'' since it is the same
on both sending and receiving hosts.
Certain other abbreviations may be permitted as special cases. For
example, at Berkeley, ARPANET hosts may be referenced without adding the
``berkeley.edu'' as long as their names do not conflict with a local host
name.
Compatibility.
Certain old address formats are converted to the new format to provide
compatibility with the previous mail system. In particular,
[email protected]
is allowed and
host:user
is converted to
user@host
to be consistent with the rcp(1) command.
Also, the syntax
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.
The current implementation is not able to route messages automatically
through the UUCP network. Until that time you must explicitly tell the
mail system which hosts to send your message through to get to your final
destination.
Case Distinctions.
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.
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@domain'' part of the address to
determine the actual sender.
Postmaster.
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.
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.
SEE ALSO
mail(1), sendmail(8);
Crocker, D. H., Standard for the Format of Arpa Internet Text Messages,
RFC822.
HISTORY
Mailaddr appeared in 4.2 BSD.
BUGS
The RFC822 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 ARPANET-style addresses do not coexist politely.
BSD 4.2 June 24, 1990 BSD 4.2