Mail keeps changing my layout.

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

conditd wrote:

In Monterey 12.0.1 Mail keeps changing my layout randomly. Is there a fix for this?

As in from " Default " - " Organize by Conversation " to " Use Column Layout " or no " Organize by Conversation "