At work, most of us use procmail to conveniently filter our mail into folders to keep a semblance of organization. I don’t know how it took me so long to find this, because I know I’ve tried to search for it before. Lo and behold, it’s located (maybe newly?) on the Tips and Tricks page. This great feature I’m talking about is the simple ability for Thunderbird to check all of my folders for new mail automatically, rather than only my Inbox. I know about folder subscriptions, the problem with those is that I have several profiles for which I’d have to do this on each of them, and I’d have to redo them every time I wiped my profile and started fresh.
Now that I’ve figured out how to do this, I’m pretty set on Thunderbird as my email client of choice.