No, this is a weird glitch happening with the email server. When I get new emails, they display as read, even before I've opened them. It's caused me to miss a few messages because there were no unread messages, and I didn't look closely enough to realize some of them were new. I'm pretty sure it has nothing to do with Thunderbird and is really just a glitch with our webmail server.
EDIT: Quick update on the overheating beast, the guy who said he can replace the thermal paste didn't have time today, so I just cracked it open myself (dear LORD it is ridiculous getting this thing open) just to check for dust clogging. I hadn't checked it in a year, after all.
As before, there was almost no dust at all inside. Only a tiny bit of extremely fine dust (the only kind that can get into this nearly airtight box). I didn't have any canned air, so I wiped off the fan blades and then just blew through the vent, dislodging the small amount that was there. It's worth noting that my apartment has a lot of (cat) hair flying around all over the place which gets into everything, but there wasn't a single strand of it inside the computer. I closed it back up (nearly as difficult as getting it open) and turned it back on, and the temperature hasn't changed a bit. Still holding steady at 50-60 degrees C (when idle). Wheeeeee!
I'll let you all know what happens when we change the thermal paste. Although the guy says he has 2 kinds and he's not sure what kind mine will need. How does one determine what type of thermal paste one needs?