All’s I got to say is — IMAP is the way to go. (This is to say that I successfully converted all my various mail archives over to proper IMAP mailboxes this weekend, and now, my web-based mail client feels a lot zippier, I can actually search my mail without having to block off an hour or two of time, and all my mail-reading clients are sharing the same archives of filed mail. This all makes me happy.)