Review for FireTray by Messo
Rated 3 out of 5 stars
Freezenig thunderbird 38.3.0 on Linux (debian based) with firetray 0.5.6.1.
Edited: Use older addon. At my case version 0.5.3.x working better, but with any problems.
To create your own collections, you must have a Mozilla Add-ons account.