Looking for a serious Windows IMAP client that doesn’t drive me nuts.

Actually, cross-platform would be even better. My gut feeling is that I’ll end up hacking on Mozilla Mail (a.k.a. Thunderbird) to meet my needs, and hopefully someone else’s.

Meantime, Eudora misses out on all sorts of things (auto-save to a remote Sent Items folder, for one); Mulberry’s interface is… interesting, plus it’s folder-list display doesn’t work for me at all; Outlook 2K isn’t actually half bad, but it’s offline support is mediocre at best.

And none of them works well in my world – where categorization / sorting happens on the server side, not at the client. That is, by the time the client sees a new email, it’s no longer in the Inbox. It’s in a folder.

I’d like that folder to be opened and highlighted, just as it would be if Outlook (e.g.) had routed it there all on its own. I’d like a standard new-mail notification. That’s all, really. OK, I’d also like full-blown disconnected-mode support, but one step at a time.

Anyone know of a client that does this right now?

Update, 2004/10/12: Thunderbird has come a long way. Search is over, I think.