What's your favorite e-mail client as far as filtering?

I'm playing catch-up on some mail accounts that haven't been checked since formatting my drive last month so there are tons of messages I need to sort through. I just watched O.E. ignore my message rules for one account and spit over 2000 messages into the inbox. I used to not have this problem with OE but I guess they updated it until they finally broke it right

What are you guys using to sort through large volume? Spam features would be cool but the primary thing I need is for it not to have a problem filtering mail sent to an account into it's own folder while sending mail from specific people sent to that account into their own folder. I'm a longtime diehard OEer because of it's Windows & Usenet integration, so anything that might help make that transition easier is a plus