Rated 5 out of 5 stars
A good extension, working as expected.
However, I did not find a button to minimize Thunderbird to tray
(this feature could be added)
Another feature request : the tray icon might be shown ONLY when the main window is hidden
(instead of always or never)
Minor bug : when installed in Thunderbird the tray tooltip says "Firefox..." instead of "Thunderbird..."
Thanks for the developper nevertheless.