Infinite loop

This is what I think happens:

• MailMate moves a message locally.
• Another client moves the same message.
• MailMate tries to synchronize the local change by moving the message on the server, but the message has now disappeared in the source mailbox.
• Instead (since this is the safest approach) MailMate tries to upload its local copy of the message to the destination mailbox on the IMAP server.
• Uploading fails because the server has a (weird) limitation that messages cannot be uploaded to the spam folder.

To fix the problem, you can locate the message(s) by enabling the UID column in the messages outline and then look for any message(s) with no UID. When located you can try deleting it. This should make MailMate upload it to the trash instead. You can also hold down ⌥ when deleting it which should delete it permanently although I'm not quite sure that works for a message in this state.

More general, it would be nice if MailMate offered some solution in the error requester. Maybe it should just offer to delete it permanently -- or maybe offer to move it (upload) to a different mailbox.

Which IMAP server has this behavior for the spam mailbox?

Benny,

Thanks––that worked like a champ and I appreciate the exceptionally fast customer support. As a refugee from Gnus who has been enamored with Gmail's keyboard efficiency, I've been a very happy customer. I use Dovecot on the server side, but haven't checked the RFC to see what the expected behavior is in this circumstance.