After the last new update 5.8 all my 12 accounts are existent, but one (my main account) had not worked and crashed K-9.
After i deleted them and created them new, i did not get the possibility to clear the trash.
The Folders… draw, trash, spam, sent i had set correctly and i had compared all the settings from the new created account to some of the old and working accounts.
I also noticed that the icons in the “special folders” are not always displayed correctly and sometimes disappear and I have to restart K-9.
So here is absolutely the worm in there!
You are lucky as in my case trash is not visible at all.
Have you set up / assigned your special folders in the account?
You can clear the trash by opening the trash folder and pressing the 3-dot overflow menu
Please read my message exactly.
In some of my accounts this is possible, but not in all.
In some of my accounts there are no option to click behind the three points to empty the trash!
All accounts are identically set and all are by the same provider.
There must be a bug in the app i think.
Sorry, I just skimmed the post because there are currently way too many questions here that ask the same thing
Could you try to manually set which folder is used as the trash folder in the account settings and restart K-9 to see if that helps?