Comment 14 for bug 367175

The volume control and brightness control and such do not use it. They only use the new black notifications, not the indicator applet. Brightness change, volume control change and such do not appear to the menu that opens when you click on the envelope (indicator applet) in the notification area. If You only want the new black notifications for thunderbird, look here: https://launchpad.net/libnotify-mozilla/+download and download the extension. It can be installed in thunderbird in the usual way, i.e. click Tools - add ons, click Install, and browse to the .xpi file contained in the downloaded tar.gz.

To my knowledge, thunderbird does not yet queue events in the indicator applet. And I agree that it should.