I tried the Mail "app" for the first time yesterday. Along with some trouble making sure the account setup worked and up to date, the way the account being tested was added to Mail, no indication of if as POP or as IMAP. There is only shown, "sync". I looked at the settings in Mail app for the test account and adjusted them so that ALL the email messages are shwon listed.
As far as I can tell, the computer has NO email messages from the test account on it. I drive into C,....comms/unistore,.... and all I find in the finest parts are a bunch of *.dat files, all or each of them very small, 1 kb or so. NO OTHER FILES FOUND. These cannot possibly be email messages.
I therefore do not really know how to use this "app" for Mail. I can see listings of the messages; all there; and I can read any that I want. BUT I do not HAVE the emails on the computer and I do not know if the setup is POP or IMAP.