Procmail is a user delivery agent. As such some people run procmail for all users which is a tad inefficient, but if you really want to do that with dmail you can use this setting
(fill in shortly)
The best way to run procmail is on a per user basis, so the user creates a .forward file entry:
In the users ~/.forward file:
|procmail -d <username>
Then procmail will run for that user but not for other users who don't want it.