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MH-ALIAS(5mh)                                                    MH-ALIAS(5mh)

NAME
       mh-alias - format of nmh email-address alias files

DESCRIPTION
       Each line of an nmh alias file takes one of the following forms:

            alias : address-group

            alias ; address-group

            < alias-file

            ; | : | # comment

       where:

            address-group  := address-list
                           |  < file

            address-list   := address
                           |  address-list, address

       Continuation  lines end with "\" followed by a newline character.  This
       also applies to comment lines.  Thus, the line following  a  "\"-termi-
       nated comment line is a continuation of that comment line.

       Alias-file and file are Unix file names.  Alias file contents are case-
       insensitive, with the exception of filesystem path names.

       If the line starts with a "<", the file named after the "<" is read for
       more  alias definitions.  The reading is done recursively, so a "<" may
       occur in the beginning of an alias file with the expected results.

       If the address-group starts with a "<", the file named after the "<" is
       read and its contents are added to the address-list for the alias.

       In match, a trailing "*" on an alias will match just about anything ap-
       propriate.

       An approximation of the way aliases are resolved at posting time is:

       1)     Build a list of all addresses from the message to be  delivered,
              eliminating duplicate addresses.

       2)     For  those addresses in the message that have no host specified,
              perform alias resolution.

       3)     For each line in the alias file, compare "alias" against all  of
              the  existing addresses.  If a match, remove the matched "alias"
              from the address list, and add each new address in the  address-
              group to the address list if it is not already on the list.  The
              alias itself is not usually  output,  rather  the  address-group
              that  the alias maps to is output instead.  If "alias" is termi-
              nated with a ";" instead of a ":", then both the "alias" and the
              address  are output in the correct format (with the alias quoted
              if necessary and the address wrapped in <>).

       Since the mh-alias file is read line by line, forward references  work,
       but backward references are not recognized.

   Example Alias File
            </etc/nmh/BBoardAliases
            sgroup: fred, fear, freida
            fred: frated AT UCI.example
            b-people: Blind List: bill, betty
            Unix-committee: <unix.aliases
            news.*: news

       The  first  line says that more aliases should immediately be read from
       the file /etc/nmh/BBoardAliases.  Next, "sgroup" is defined as an alias
       for three names, and one of them, "fred", is a forward reference to an-
       other alias for "frated AT UCI.example".

       The alias "b-people" is a  blind  list  which  includes  the  addresses
       "bill"  and  "betty"; the message will be delivered to those addresses,
       but the message header will show only "Blind  List:  ;"  (not  the  ad-
       dresses).   The  alias must not be terminated with, or contain, a semi-
       colon.  Note that blind lists are not supported with the  sendmail/pipe
       mail transport method.

       The  definition  of  "Unix-committee"  is  given  by  reading  the file
       unix.aliases in the user's nmh directory.

       Lastly, "news.anything" is aliased to "news"; the full stop is just an-
       other literal character.

PROFILE COMPONENTS
       Aliasfile:          Default alias file.

FILES
       /etc/nmh/MailAliases
                           System-wide default alias file.

SEE ALSO
       ali(1), send(1), whom(1), getgrent(3), getpwent(3), post(8)

BUGS
       Although  the  forward-referencing  semantics of mh-alias files prevent
       recursion, the alias-file directive may defeat this.  Since the  number
       of  file  descriptors is finite, such infinite recursion will terminate
       with a meaningless diagnostic when all the fds are used up.

       Earlier versions of this man page showed a semicolon at the end of  the
       blind  list  example.   That  caused  the preceding alias to not be ex-
       panded.  There must not be a semicolon at the end of,  or  within,  the
       address  group  of a blind list.  post will append the semicolon to the
       blind list name.

nmh-1.7.1                         2014-04-18                     MH-ALIAS(5mh)