Does anyone know which files you need to move to manually transfer POP Mail data from one system to another. I routinely do this between my desktop and laptop.
It used to be
user/library/accounts
user/library/application support/mail
user/library/containers/com.apple.mail
user/library/preferences/com.apple.mail.plist
user/library/mail
But with Monterey it seems that the storage locations have changed
I don’t think the top-level folders have changed in Monterey. I general, I do not recommend trying to copy/replace Mail’s files, especially if the Macs have different versions. You could use an IMAP account instead of POP to have Mail automatically sync the messages between devices. Or, Mail provides commands for exporting and importing mailboxes. Or you could put the messages to share in an EagleFiler library and copy/sync that.