OK, I managed to figure it out, notifications were being sent by a Thunderbird addon 'Gnome Integration'. Dissabling/configuring this addon solved the issue.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1510907 Title: Thunderbird Gnome Notification Deactivation Ignored, Wily 15.10 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1510907/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs