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 “\”-terminated 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 appropriate.

       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
              terminated  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@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
       another alias for “frated@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  addresses).
       The  alias must not be terminated with, or contain, a semicolon.  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 another 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 expanded.  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-1.8                                            2014-04-18                                      MH-ALIAS(5mh)