Linux Mail Server

Creating an m4 DOMAIN File:

The domain directory is intended for m4 source files that contain information specific to your domain. This is a perfect place to put the commands that rewrite the hostname to the domain name on outbound mail, so we create a new m4 macro file in the domain directory and call it foobirds.m4. We begin by changing to the ../domain directory and copying the file generic.m4 to foobirds.m4 to act as a starting point for the configuration. The listing below shows these steps.

# cd /usr/share/sendmail-cf/domain

				# cp generic.m4 foobirds.m4

				# chmod 644 foobirds.m4

				# tail -6 foobirds.m4

				VERSIONID(`$Id: generic.m4,v 8.15 1999/04/04 00:51:09 ca Exp $')

				define(`confFORWARD_PATH', `$z/.forward.$w+$h:$z/.forward+$h

				Ä:$z/.forward.$w:$z/.

				forward')dnl

				define(`confMAX_HEADERS_LENGTH', `32768')dnl

				FEATURE(`redirect')dnl

				FEATURE(`use_cw_file')dnl

				EXPOSED_USER(`root')

After copying generic.m4 to foobirds.m4, use the chmod command to set the file access permissions for the new file. (On some systems, the files in the domain directory are read-only.) Make the file read and write for the owner, and read-only for the group and the world.

The tail command displays the last six lines in the newly created foobirds.m4 file. (All of the lines before this are comments that are of no interest for this discussion.) You have already seen the VERSIONID macro. The first new line is the macro that defines confFORWARD_PATH, which tells sendmail where to look for the user's .forward file. The $z and the $w sendmail variables were described earlier in the discussion of the sendmail.cf ForwardPath option, which contained the two paths $z/.forward.$w:$z/.forward. Those two paths are the default value for confFORWARD_PATH. The define in the previous listing increases the complexity of the.forward path list by adding the value $z/.forward.$w+$h:$z/.forward+$h to the default search list. The $z and $w variables serve the same purpose as before. The $h variable contains the detail value when the user+detail addressing syntax is used, and procmail is used as the local mailer. We know that procmail is being used as the local mailer from the local_procmail feature in the linux.m4 OSTYPE file. Given this specific configuration, local mail on a host named egret addressed to craig+tux would prepend the following. forward search path to the standard path:/home/craig/.forward.egret+tux:/home/craig/.forward+tux. Even though user+detail addressing is rarely used, we decide to keep this define in the configuration because we plan to use procmail as the local mailer.

Next: Creating an m4 DOMAIN File (Part 2)