I started out with procmail. Then I discovered mailagent. So I rewired everything to use that, and then have been slowly patching my ".rules" file, which is now up
to 686 lines. But then mailagent got to be too slow for the 1000 or so pieces of email I get every day, so I added a few very-early filters in procmail. Mailagent handles the autoreplies and forwards by itself, but for mail I need to see, delivers to about 50 different ".spool" files, which are then read by GNUS and sorted into their own bins (I don't do any further sorting in GNUS).
When I get about a dozen more TUITs, I'm going to completely eliminate old dead Mailagent with my own tools. There's still things done by mailagent trivially
that the Mail::Audit (and friends) packages don't do, so I've got to handroll
some stuff no matter what. I figure it'll take about a day or so to get right.
-- Randal L. Schwartz, Perl hacker