Rated 5 out of 5 stars

The add-on works great, but it has one limitation that I can't get around. The "Save Message as File" option saves the file without national diacritics. i.e. e.g. replaces "ą" with "a". Can you do something about it?

This review is for a previous version of the add-on (3.6.1). 

replacing a safety feature by the original author - can you raise a github issue / feature request for allowing other characters?
https://github.com/RealRaven2000/FiltaQuilla/issues