I use Pine. Unless I'm on my MacOSX, when I use Apple Mail, which is surprisingly nice. Something to note is that most IMAP searches are done on the server, so ``fast searching'' may not be a feature of the client, except in offline mode. You might want to take a look at Mulberry. It's a very nice client, but it's very quirky (that is, it doesn't do things in the same way as other email clients).