Mac Mail error occurred while moving messages to mailbox

An error occurred while moving messages to mailbox “”.

After more than a year, I finally figured out the Mac Mail error that I was getting when deleting a email message.

Just make sure that your Accounts > Mailbox Behaviors have their Mailboxes set. In my case they were blank. Setting them to the right folders (as seen below) fixed the An error occurred while moving messages to mailbox “”. error and my sanity has been regained.

All the google "fixes" said it had to do with going to selecting a mailbox, then going to Mailbox > Use This Mailbox As. Well, I don't have "Use This Mailbox As" in the menu. So I gave up until I looked into it more and found the Mailbox Behaviors tabs and fixed it. Now I can delete emails again!

I hope this saves someone the pain that I suffered.