Rated 5 out of 5 stars

I'm on a Windows machine. On versions 38 and below, the utility RBTray (available on SourceForge) worked to minimize Thunderbird to the tray. With the upgrade to version 45 it stopped.

MinimizeToTray works with Thunderbird 45. After you install the Add-on, go to its options. In Minimize to tray, I have 'When minimizing' selected. When I minimize Thunderbird, it properly goes down to the system tray.

This review is for a previous version of the add-on (1.1.2.1-signed.1-signed).