Review for Windows Taskbar Unread Badge by Thecoalcracker
Rated 5 out of 5 stars
This addon is better than the built in version in tb91. It appears tb91 only counts unread emails in primary folders (inbox) and does not include sub-folders. Many of my emails are filtered into such sub-folders, making the built in almost useless.
To create your own collections, you must have a Mozilla Add-ons account.