I somehow have multiple accounts for the same email address - they both receive messages sent to that address but one (the POP) has hundreds of emails in the Inbox and Sent, going back years and the other (the IMAP) has four in, going back a week, and none out.
In Mail>Preferences>Accounts they both appear, one with a grey IMAP beneath it and one with a grey POP.
In Settings>Internet Accounts they also both appear, this time with a grey Mail and a grey Notes beneath them.
Is there any reason why I should want this setup, and what is the best way to rationalise it (which I would like to do by removing the POP, but without losing emails)?