Procmail might serve your needs better, actually, as it allows some greater flexibility. It works like filters for netscape's mail client, but is configured at the server level via a text file in the user's home directory. (And it is a lot easier than it looks). There's a pretty solid tutorial for it here: at infinite ink. Most *nix systems come with procmail installed.

I don't know your requirements exactly. How are you getting the mail in a particular folder to that particular folder? Is it possible that that system could forward the mail in addition to sorting it?