Apple email
I have both a POP and iMap email accounts (same address). How to change to use only iMap and save the POP emails at the same time. OS 12 Big Sur on 27" iMac. Backed up by Time Machine.
iMac 27″, macOS 10.13
Once an email is received, it should not be affected by changes in a mail account.
I'd suggest you completely remove the email accounts and recreate the one you want.
You might want to drag and drop all critical emails into a folder on your drive beforehand just to be on the safe side.
