The K9 Mail app used to be able to delete all messages and reset storage for an account. That functionality was removed I guess because I can’t find it any longer. Why was that removed? Storage for an account is corrupted and the only way I can fix it is to delete and recreate the account. Can you please put the functionality back? I donated!
Are you referring to the “Clear local messages” option? If so, select the account in question, then select the folder icon at the bottom (right) on the screen - to the left of the gear. You will then get a list of the folders for that account. Select the desired folder (likely the Inbox) and then the three vertical buttons in the upper right. You should then see the “Clear local messages” option.
Before recent design changes there were two options: clear messages and recreate data. I was able to find the clear message function, though getting there was slightly different than you described. It would be nice to have the recreate function again. In this case I had many folder and had to delete messages in each. If the database is corrupted that will not necessarily fix it. Thanks for the info.