iMac (Retina 5K, 27-inch, 2017), macOS Mojave 10.14.6, Mail 12.4
My Mail app has gotten into a seemingly infinite loop, continuously reporting that
The message "" could not be moved to the mailbox " 8. August, John_In archives — FlashNet" The IMAP command "APPEND" (to Archives/Current year archives/John_In archives/ 8. August, John_in archives) failed with server error: APPEND Contains Deleted flag.
Because these messages appear one right after another when I dismiss them, Mail is rendered unusable. HELP!!!