Rated 3 out of 5 stars

per andrybak el feb. 4, 2023 ·

The addon only wraps the lines visually. The actual outgoing emails will still have very long lines, which is not good for plain text mailing lists.

This review is for a previous version of the add-on (1.4.1). 

per Jan Kiszka (desenvolupador) a feb. 4, 2023 ·

Did you "make sure that "mailnews.send_plaintext_flowed" is disabled" (see add-on description)? If so, please share more details about your setup.
Your use case is also my use case and the primary reason why I'm maintaining this.