When I delete an email I want it gone, immediately. Not copied to Trash from where I need to cleanup later. Likewise when I send email I do not want a copy stored in a Sent folder, I’ll CC myself on the rare occasions when I need to keep a copy.
This works fine with other mail clients like Thunderbird on Windows and Linux, but in K9 on Android (version 18) I have gone to the Settings->Account->Folders, and set Sent folder to “None” and Deleted Items folder to “None”. This works for a short while (an hour or so), but then K9 resets these to “Automatic(Sent)” and “Automatic(Trash)” and I suddenly find these folders created and cluttered up with unwanted messages, which is absolutely infuriating. How do I stop K9 from resetting these values?
There’s a TBA bug report open on github discussing the trash folder assignment reverting after being set to none. You should consider adding your findings to that ticket, linked below.