What follows in a recipe to extract the finest ham from spam. (note however, that the author no longer uses this recipe as published)
Ingredients

procmail
spamassassin
DreamHost Unix shell account
Gmail account

Summary
We’ll forward your public email address (public@mydomain.com) to your server shell account (shellaccount@sjov.dreamhost.com), where we’ll filter your mail through procmail and SpamAssassin, and depending on the results, forward [...]