Sudden sync failure between iPhone and Mac.
I've seen several questions like this but can't seem to find a similar situation. Overnight it seems there has been a syncing issue between my Mac and iPhone. Previously, all emails (outgoing and incoming via IMAP accounts) were appearing on both the Mac and iPhone. Now, emails are only appearing on the iPhone. I have confirmed that the passwords on the IMAP accounts are correct and the Tools/Accounts indicates they are connected. The only thing recent change I can think of is that I recently updated my Apple Watch and have received the on-screen notices that the Watch has been added to the syncing devices.
I've seen the answers with regard to logging out of iCloud, checking the IMAP passwords etc., but none of that seems to be the solution.
MacBook Pro 15″, macOS 11.4