Rated 3 out of 5 stars

It does not work at TB78.10.0(64bit).

This review is for a previous version of the add-on (6.3.2). 

It does(!) work in 78.10.0 / 64-Bit. Please report your problem or support request in the forum https://www.thunderbird-mail.de/forum/board/82-allow-html-temp/ or at GitLab https://gitlab.com/ThunderbirdMailDE/allow-html-temp/-/issues