I see a few other users have this problem too, as far back as 2015 - 2016. However, not many users have reported this issue and so far I have not received an answer (3 months). How can this problem be approached and fixed – does someone in the Thunderbird team have insight on the issue? There is obviously a mechanism that deletes drafts from the draft folder once messages are sent, but why does this mechanism sometimes ''not'' work, and how can it be made to work again?