Review for Gnome Integration by IBBoard
Rated 5 out of 5 stars
Works well, and nice to see notifications through the proper system (I'm using openSUSE with notify-osd bodged in as a replacement for notification-daemon). I thought there used to be something similar that you could set up manually, but I couldn't find anything that worked with Thunderbird 3.
Only minor issue I noticed was with translation - there is a "y" in the HTML list for the message where it should be "and" in English :)
To create your own collections, you must have a Mozilla Add-ons account.