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REWRITE(6)                       Games Manual                       REWRITE(6)

       rewrite - mail rewrite rules


       Mail(1)  uses  rewrite rules to convert mail destinations into commands
       used to dispose of the mail.  Each line of the file is a  rule.   Blank
       lines and lines beginning with # are ignored.

       Each rewriting rule consists of (up to) 4 strings:

              A  regular expression in the style of regexp(6).  The pattern is
              applied to mail destination addresses.   The  pattern  match  is
              case-insensitive and must match the entire address.

       type   The type of rule; see below.

       arg1   An ed(1) style replacement string, with \n standing for the text
              matched by the nth parenthesized subpattern.

       arg2   Another ed(1) style replacement string.

       In each of these fields the substring \s is replaced by the login id of
       the  sender  and  the substring \l is replaced by the name of the local

       When delivering a message, mail starts with the first rule and  contin-
       ues  down the list until a pattern matches the destination address.  It
       then performs one of the following actions depending on the type of the

       >>>>     Append  the  mail  to the file indicated by expanding arg1, pro-
              vided that file appears to be a valid mailbox.

       |      Pipe the mail through the command formed from concatenating  the
              expanded arg1 and arg2.

       alias  Replace  the  address  by the address(es) specified by expanding
              arg1 and recur.

              Replace the address by the address(es)  output  by  the  command
              formed by expanding arg1 and recur.

       Mail expands the addresses recursively until each address has matched a
       >>>> or | rule or until the recursion depth indicates  a  rewriting  loop
       (currently 32).

       If  mail(1)  is called with more than one address and several addresses
       match | rules and result in the same  expanded  arg1,  the  message  is
       delivered  to all those addresses by a single command, composed by con-
       catenating the common expanded arg1 and each expanded arg2.  This  mail
       bundling is performed to reduce the number of times the same message is
       transmitted across a network.  For example, with the following  rewrite

          ([^!]*.att.com)!(.*)  |  "/mail/lib/qmail '\s' 'net!\1'" "'\2'"

       if user presotto runs the command

          % mail research.att.com!ken research.att.com!rob

       there will follow only one execution of the command

          /mail/lib/qmail presotto net!research.att.com ken rob

       Here /mail/lib/qmail is an rc(1) script used for locally queuing remote

       In the event of an error, the disposition of the mail  depends  on  the
       name  of  the  command executing the rewrite.  If the command is called
       mail and is run by $user, the command will print an error  and  deposit
       the  message  in /mail/box/$user/dead.letter.  If the command is called
       rmail, usually because it was invoked to deliver mail arriving over the
       network, the message will be returned to the sender.  The returned mes-
       sage will appear to have been sent by user postmaster.