The Macworld site has posted a really good review of MailMate by Nathan Alderman awarding it 4 out of 5 mice. I couldn’t have written it much better myself. For comparison, Thunderbird got 3.5 of 5 mice and Apple Mail got 4.5 of 5 mice, but take into account that the “cons” of MailMate were “no POP or Exchange support” and “designed for power users”.
The review on the subject of searching/smart mailboxes:
As email search abilities go, this seems less like bringing a gun to a knife fight, and more like thundering into that particular duel at the controls of a helicopter gunship.
As any software developer I most often receive feedback from users with problems, so this was nice to read:
Needless to say, the program never crashed, glitched, or gave me any sort of trouble during my tests. MailMate does not know weakness.