Rated 5 out of 5 stars

This is really a very useful addon. Unfortunately, it does not work anymore with Thunderbird 57.0b1. I had to start Thunderbird in safe-mode and deactivate it.

This review is for a previous version of the add-on (4.7.1). 

Please check here:

It's complicated but there are some explanations and a working test version available there.