Rated 5 out of 5 stars

This addon works great for me with Thunderbird 45.3.0. It provides the functionality that should be in the core code.

I found your addon from this post in the Mozilla support forum:
https://support.mozilla.org/en-US/questions/1132064#answer-921877

Afterwards I found the FOURTEEN year old bug in Bugzilla about the problem:
https://bugzilla.mozilla.org/show_bug.cgi?id=177175

Thank you again for providing a way round an issue that Mozilla obviously do not have any care about!

This review is for a previous version of the add-on (1.6.1-signed.1-signed).