mail addressing description
Mail addresses are based on RFC 822 except
for the limitations listed at the end of this manual page.
These addresses are in the
where a 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 yoyodyne gateway, after which it should go
to the local host fred. When the message reaches
fred it is delivered to the user stevea.
Unlike some other forms of addressing, this does not imply
any routing. Thus, although this address is specified as an
RFC 822 address, it might travel by an alternate
route if that were more convenient or efficient. For
example, at yoyodyne, the associated message would probably
go directly to fred over the Ethernet rather than
going via the yoyodyne mail 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 ``barney.yoyodyne.com'' could send to
``stevea@fred'' without adding the ``yoyodyne.com'' since
it is the same on both sending and receiving hosts.
Certain other abbreviations may be permitted as special
cases. For example, at yoyodyne, Internet hosts may be
referenced without adding the ``yoyodyne.com'' as long as
their names do not conflict with a local host name.
Certain old address formats are converted to the new format
to provide compatibility with the previous mail system. In
particular, user@host.ARPA is
allowed and host:user is converted to
user@host to be consistent with the
Also, the syntax host!user is converted
This is normally converted back to the ``host!user'' form
before being sent on for compatibility with older UUCP
The current implementation is unable 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
Domain names (that is, anything after the ``@'' sign)
may be given in any mixture of upper- and lowercase with
the exception of UUCP hostnames. Most hosts accept any
combination of case in user names, with the notable
exception of MULTICS sites.
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:
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.
Every site is required to have a user or user alias
designated ``postmaster'' 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 and may not be supported at all
sites. For example, messages to CSNET or
BITNET sites can often be sent to
RFC 822, RFC 974
The RFC 822 group syntax
is not supported except in the special case of
``group:;'' because of a conflict with old
UUCP- and RFC 822-style addresses do not coexist
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004