Mailbox Alert update; 0.16 has been released through addons.mozilla.org.
It contains fixes for a number of issues people had with 0.15 (the biggest one being that it didn’t work consistently with the internal messaging system across several thunderbird versions).
However, in my enthusiasm, I uploaded a wrong file to AMO, and it did not contain a few important fixes and cleanups.
Unfortunately, these weren’t considered important enough to hold off releasing it by the reviewer (since in most cases it does work). I immediately fixed the issues (by changing the version to 0.16.1 and uploading the version I should have sent in the first place), but I’m holding off the version here until that one has been reviewed.
I hope this will be done soon, and I hope this was just some fallout from the cursed 0.15 release, and 0.16 will be nothing but ponies and candysticks from now on.