The extension works perfectly when I close Thunderbird.
However when I minimize the window, it minimizes like a normal application, instead of going to the tray.
I have tried setttings preferences to both "When minimizing" and "Instead of closing and when minimizing". Neither one results in minimization to tray.
I'm using Ubuntu 16.04 with Cinnamon (not Unity).
The extension works perfectly when I close Thunderbird. However when I minimize the window, it minimizes like a normal application, instead of going to the tray.
I have tried setttings preferences to both "When minimizing" and "Instead of closing and when minimizing". Neither one results in minimization to tray.