I recently needed to send my Windows 10 laptop away for repair and used a slightly older reserve laptop to check my IMAP emails. Now when I am back on the repaired laptop I find a 'ghost' deleted folder (which I cannot delete) and sometimes I get an error message about a missing "trash" folder too - although I have a perfectly good trash folder and a working deleted folder... I have been into the account settings area and everything seems to be in order... I can delete the errant "deleted" folder, but when I restart Thunderbird (91.1.2 (64-bit)) the empty weird "deleted" folder comes back -- see screen grab! The reserve laptop is no longer in use. Switched off. ????