I use Ubuntu 16.04 with Thunderbird 45.4. When I receive a new email, I want the Thunderbird tray icon in the right upper corner to change (so that I know that I have an unread email). I saw somewhere that the icon should turn into the blue color. But my icon remains the same all the time. How can I change that?
tltr: Why does the Thunderbird tray icon not turn blue when a new email arrives?
EDIT: Is it possible that the method described at this old link Why won't Thunderbird report notifications to the indicator-applet on 12.04? would help?
The only reason I don't want to try what is described in the link above immediately is that I don't know how to undo the changes performed by "sudo apt-get install notification-daemon esound python-notify" (I am new to Ubuntu). If someone tells me how undo the changes then I will try and see.
SOLVED: It turned out that my Thunderbird tray icon did never turn blue because a Firefox extension Gmail Notifier accesses the new emails first. When I turnd this extension off, everything started to work well.