You know what rox? procmail does. When I don't want to recieve mail when certainpeople post replies to my livejournal entries defending ad-hominem attacks against my girlfriend because she exposed them as the livejournal spammers they truly are.
From email@example.com Tue Jan 8 03:11:12 2002 Subject: Reply to your comment... Folder: /dev/null 4569
As I hear so often on NANOG, procmail is your friend.