Since this thread is (probably predictably) "what I don't like about Thunderbird", I don't have the problems that others are having with the search algorithm per se; but, after finding mails, it refuses to show them to me. It correctly shows me snippets from the mails that it finds, but, when I try to access those mails, it just shows me a blank window.

(It also refuses to acknowledge deleted and created folders on my work account, but, not knowing the actual cause, I am very happy to suppose that the blame lies on some administrator at work making some hostile-to-non-Outlook-users change in OWA setting.)