Sendmail Virtual Domains

        -------------------------------------------------------------

This document contains an outline on how to alias full user@domain to
another local user.

With the Cw directive, you can let Sendmail deliver mail for the specified
domain. The disadvantage to this approach is that you cannot alias the same
login to different domains; for example, webmaster@dom1.com would go to the
same person as webmaster@dom2.com. Same goes for sales, info and other
important aliases you can sell.

For it to work, you need to have a Sendmail with Berkeley db(1) support.
This means compilation with -DNEWDB and linking with -ldb. See the Makefile
in the src/obj* directory for more information.

In /etc/sendmail.cf, you need to specify a db file for the maildomain
lookup:

        Kmaildomains hash /etc/maildomains.db

Also, the following rule needs to be added:

###################################################################
###  Ruleset 98 -- local part of ruleset zero (can be null)     ###
###################################################################

# Try to remap domains via /etc/maildomains.

S98
R$+ < @ $+ . >          $: $1 < @ $2 > .
R$+ < @ $+ > $*         $: $(maildomains $1@$2 $: $1 < @ $2 > $3 $)
R$+ < @ $+ > $*         $: $(maildomains $2 $: $1 < @ $2 > $3 $)
R$+ < @ $+ > .          $: $1 < @ $2 . >

It is possible to integrate all this into the m4 system Sendmail uses to
generate its config file. My config.mc is available online. (You can use the
LOCAL_RULE_0 directive to set up S98.)
I have also modified some things in the cf/ directory, most notably the
handling of so-called plussed users (I use = instead), and some comments for
clarity.

/etc/maildomains contains the following fields, separated by tabs:

        webmaster@dom1.com      userthatdoestheirwww
        sales@dom2.com          salesdroidfordom2
        dom2.com                dom2owner

This means, that all mail to webmaster@dom1.com will go to
userthatdoestheirwww. Same for sales@dom2.com.
All mail addressed to anything@dom2.com will be dropped into dom2owner's
mailbox.

To create the necessary db(1) files, run the following command:

        # makemap hash /etc/maildomains.db < maildomains

Instead of hash, you can also specify btree. You will also have to change
this in /etc/sendmail.cf.
Note: dbm does not work in this case!

Note that procmail(1) can be a very nice thing to have: you can mail to
user+webmaster, for example, and that user can sort his/her mail into
different mailboxes, using procmail(1).
(If you have applied a part of my diff, it would of course be
user=webmaster.)

----------------------------------------------------------------------------
 [-Niels' Home Page-]           Comments  [-Mail-] PGP Key        [-PI NL-]