This is still happening with Ubuntu 18.04 (Gnome) and Thunderbird 60.5.1. If I setup a message filter to move emails to another folder and mark them as read, then the Thunderbird icon in the docker shows unread emails, even though all my emails are read.
This is still happening with Ubuntu 18.04 (Gnome) and Thunderbird 60.5.1. If I setup a message filter to move emails to another folder and mark them as read, then the Thunderbird icon in the docker shows unread emails, even though all my emails are read.