MAILADDR(7)             COMMAND REFERENCE             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:

          eric@monet.Berkeley.ARPA

     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, 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.ARPA could send to eric@monet without
     adding the .Berkeley.ARPA since it is the same on both
     sending and receiving hosts.

     Certain other abbreviations may be permitted as special
     cases.  For example, ARPANET hosts can be referenced without
     adding the .ARPA 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,





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MAILADDR(7)             COMMAND REFERENCE             MAILADDR(7)



          host:user

     is converted to:

          user@host

     to be consistent with the rcp(1n) command.

     Also, the syntax:

          host!user

     is converted to:

          user@host.UUCP

     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 the message
     routing is automated, 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 uppercase and lowercase letters with
     the exception of UUCP host names.  Most hosts accept any
     mixture of case in user names, with the notable exception of
     MULTICS sites.

     Differences with ARPA Protocols

     Although the UTek addressing scheme is based on the ARPA
     mail addressing protocols, there are some significant
     differences.

     At the time of this writing the only ``top level'' domain
     defined by ARPA is the .ARPA domain itself.  This is further
     restricted to having only one level of host specifier.  That
     is, the only addresses that ARPA accepts at this time must
     be in the format user@host.ARPA (where host is one word).
     In particular, addresses such as:

          eric@monet.Berkeley.ARPA

     are not currently legal under the ARPA protocols.  For this
     reason, these addresses are converted to a different format
     on output to the ARPANET, typically:



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MAILADDR(7)             COMMAND REFERENCE             MAILADDR(7)



          eric%monet@Berkeley.ARPA

     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.
     An address that shows 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@host
     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.

     CSNET

     Messages to CSNET sites can be sent to ``user.host@UDel-
     Relay''.

SEE ALSO
     mail(1mh) and sendmail(8mh).




















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