Review for Windows Taskbar Unread Badge by Jerl
Rated 4 out of 5 stars
This is a great step in the right direction, but unfortunately its functionally useless to me because of its inability to ignore certain inboxes.
I also use Thunderbird for several YouTube and comic RSS feeds, many of which have 10+ unread entries at any given time. Because of this, the icon perpetually shows 99+ messages, even if there's no new messages in my email inbox, which is what I'm actually interested in seeing.
This probably isn't the scenario for the majority of people interested in this add-on, though, and it seems to do the job well if you keep caught up on your RSS feeds or if you only use Thunderbird for email.
To create your own collections, you must have a Mozilla Add-ons account.