Error Message: could not be moved to the mailbox "mac mail"

Hello klezmire,

This error may be caused by the Mail app being unable to reach the mailbox your'e attempting to move messages into. To help resolve this issue, check your Mailbox rules to make sure there aren't any conflicts as shown in this article: Use rules to manage emails you receive in Mail on Mac - Apple Support

1. In the Mail app  on your Mac, choose Mail > Settings, then click Rules.

2. To review an example of a rule, select a provided rule, then click Edit. To close the rule, click Cancel.

Best Regards.