Rated 5 out of 5 stars

totally great! This is a must-have extension :-) Some room for improvement:
* include that by default in Thunderbird
* use OS-specific paths, too - example: ~/Library/Images/People/ can contain image files on MacOS with filenames identical to the corresponding e-mail addresses (suffix .tiff) which are then displayed in the native app. These could also be used here (?)
* (fixed issue)

This review is for a previous version of the add-on (1.2.2). 

Hi, thanks for your feedback!
- For the first point, I'm afraid this is not in my power :)
- OS-specific paths can lead to compatibility issues. However you can use the address book to override automatic profile pictures
- This issue is now fixed in the latest version (1.2.4)