Unfortunately, I dislike thunderbird with a passion. In my anecdotal experience, its search is terrible - not to mention that there are two of it: a search option in the top panel that misses about 50% of relevant messages, and a very featureful search option buried within the menu bar that misses about 20% of relevant messages. Out of necessity, I've trained myself to just reboot to Windows any time I really need to find a particular email that I know I have somewhere. I also don't particularly like Thunderbird's UI, but that is something I'm able to compromise on.
Not meant to be a rant, but rather: please, someone, is this really the best we have?