Rated 5 out of 5 stars
Awesome add-on, this is right now probably the best way of configuring how Thunderbird notifications are handled.
Feature request: an additional option provided by this add-on could be to raise the urgent notification flag when new messages arrive. This effects e.g. the i3 wm, where the workspace indicator should be highlighted on new messages (but by default is not).
GNotify already provides functionality for raising the urgent notification flag (but it is more than just ticking an option in the settings):
having wmcrtl installed, setting the notification engine to "Custom", and executing this custom command when new mails arrive:
wmctrl -r "Thunderbird" -b toggle,demands_attention