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MAILADDR(7)            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

                 ericATmonet.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 was 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.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, at Berkeley 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 par-
       ticular,

                 host:user

       is converted to

                 user@host

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

       Also, the syntax:

                 host!user

       is converted to:

                 userAThost.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 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  mixture  of  case  in  user
       names, with the notable exception of MULTICS sites.

       Differences  with  ARPA Protocols.  Although the UNIX addressing scheme
       is based on the ARPA mail addressing protocols, there are some signifi-
       cant 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 ``userAThost.ARPA''
       (where ``host'' is one word).  In particular, addresses such as:

                 ericATmonet.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:

                 eric%monetATBerkeley.ARPA

       Route-addrs.   Under  some circumstances it may be necessary to route a
       message through several hosts to get it to the final destination.  Nor-
       mally 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 gen-
       erally augmented by the software at each host.  It is generally  possi-
       ble  to  ignore all but the ``user@host'' part of the address to deter-
       mine the actual sender.

       Postmaster.  Every site is required to have a user or user alias desig-
       nated  ``postmaster''  to  which  problems  with the mail system may be
       addressed.

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

BERKELEY
       The following comments apply only to the Berkeley environment.

       Host  Names.  Many of the old familiar host names are being phased out.
       In particular, single character names as used in Berknet are incompati-
       ble  with the larger world of which Berkeley is now a member.  For this
       reason the following names are being obsoleted.  You should notify  any
       correspondents of your new address as soon as possible.

                 OLD            NEW                   j ingvax       ucbingres
                 p              ucbcad                  r arpavax      ucbarpa
                 v csvax        ucbernie                 n              ucbkim
                 y              ucbcory

       The old addresses will be rejected as unknown  hosts  sometime  in  the
       near future.

       What's  My  Address?   If  you  are on a local machine, say monet, your
       address is

                   yournameATmonet.ARPA

       However, since most of the world does not  have  the  new  software  in
       place  yet,  you  will  have  to give correspondents slightly different
       addresses.  From the ARPANET, your address would be:

                   yourname%monetATBerkeley.ARPA

       From UUCP, your address would be:

                   ucbvax!yourname%monet

       Computer Center.  The Berkeley Computer Center is  in  a  subdomain  of
       Berkeley.  Messages to the computer center should be addressed to:

                   user%host.CCATBerkeley.ARPA

       The alternate syntax:

                   userAThost.CC

       may be used if the message is sent from inside Berkeley.

       For  the time being Computer Center hosts are known within the Berkeley
       domain, i.e., the ``.CC'' is optional.  However, it is likely that this
       situation will change with time as both the Computer Science department
       and the Computer Center grow.

       Bitnet.  Hosts on bitnet may be accessed using:

                   userAThost.BITNET

SEE ALSO
       mail(1), sendmail(8); Crocker, D. H., Standard for the Format  of  Arpa
       Internet Text Messages, RFC822.



4th Berkeley Distribution                                          MAILADDR(7)