I have had this issue for a while, re-booted as suggested on a similar thread in 2022 but the issue persists. It's very concerning. Please note that this happens only on devices using Big Sure, I am on the previous OS on another iMac and there is no issue there.
Thank you in advance for any help.
The usual fix is to rebuild the affected Mailbox: Rebuild mailboxes in Mail on Mac - Apple Support.
You can rebuild any Mailbox including local "On My Mac", Mailboxes, Inbox, Trash, Sent, etc. I recommend rebuilding all of them.
The usual fix is to rebuild the affected Mailbox: Rebuild mailboxes in Mail on Mac - Apple Support.
You can rebuild any Mailbox including local "On My Mac", Mailboxes, Inbox, Trash, Sent, etc. I recommend rebuilding all of them.
Apple Mail Error "message --- could not be moved to mailbox
