I have a fastmail IMAP account and use Mail on the Mac. The past few days this error message keeps coming up and it is making Mail unusable for me. I have tried deleting and re-adding the account but it hasn't fix the problem. Mail on my iPad and iPhone is working find without any issues. The error message is: The IMAP command “APPEND” (to INBOX.Read Receipts) failed with server error: Too many identical emails.
Any ideas on how to fix?
Any ideas on how to fix?