Rated 5 out of 5 stars

Works fine with Thunderbird 5 (if you manually set the compatibility). You can add your own icons for newer programs that aren't supported out-of-the-box, like Outlook 2011 for Mac or mail from the iPad. See their web site for instructions on manually adding your own icons. All-in-all, pretty awesome add-on.

This review is for a previous version of the add-on (1.6.6).