Deleting an old POP account from Mail

When I started a domain the mail server there was POP only. Eventually it was upgraded to IMAP and I made a new account in Apple’s Mail app with the IMAP details. I disabled the POP account in Mail.

I tried to delete the old disabled POP account today, but got all sorts of warnings from Mail that all it’s messages and Mailboxes would be deleted. I have archives of old mails going back years stored on iCloud, and don’t want to lose them. Given that Mail will still have an account with the same e-mail address (just with IMAP server settings) I think it will be safe to delete the old account now. Am I right?