Rated 5 out of 5 stars

Works on Gnome 3.16 + Arch Linux + Thunderbird 38 Beta.

Doesn't have the fancy Mailbox icon that FireTray has, however it seems to be simple and effective, and unlike FireTray it's set to "double-click" to restore - which is more consistent with other Tray icons.

This review is for a previous version of the add-on (1.1.2.1-signed.1-signed).