mail addressing description
Mail addresses are based on the ARPANET protocol listed in
These addresses are in the general format:
where domain is a hierarchical, dot-separated list
of subdomains. For
example, the address
is normally interpreted from right to left: the message should go to the
ARPA name tables (which do not correspond exactly to the physical
then to the Berkeley gateway, after which it should go to the local host
When the message reaches
it is delivered to the user
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 alternative route if that were more convenient or efficient.
For example, at Berkeley, the associated message would probably go directly
over the Ethernet rather than going via the Berkeley ARPANET gateway.
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
could send to
without adding the
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
as long as their names do not conflict with a local hostname.
Certain old address formats are converted to the new format to provide
compatibility with the previous mail system. In particular:
is allowed, and
is converted to
in order to be consistent with the
Also, the syntax
is converted to:
This is normally converted back to the
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.
Domain names (that is, anything after the
``@'') may be given in any mixture
of upper and lower case with the exception of UUCP hostnames.
accept any combination of case in user names, with the notable exception of
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
These use the syntax:
This specifies that the message should be sent to
from there to
and finally to
This path is forced even if there is a more efficient path to
Route-addrs occur frequently on return addresses, since these are usually
augmented by the software at each host. It is generally possible to ignore
all but the
part of the address to determine the actual sender.
Every site is required to have a user or user alias designated
to which problems with the mail system may be addressed.
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
be supported at all sites. For example, messages to CSNET or
can often be sent to
The RFC 822 group syntax
is not supported except in the special case of
because of a conflict with old berknet-style addresses.
UUCP and ARPANET-style addresses do not coexist politely.
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003