Can Dovecot honor Outlook's "leave mail on server for X days" setting?

I googled around for a quite bit but surprisingly came up empty for an answer to this question which I'm sure has been broached before.

I've got a linux box running dovecot/postfix using maildir format. I was surprised to learn that a client that had many GBs of email was running POP3, not IMAP. It turns out they had a setting to delete POP3 mail after X days turned on but it just went ignored.

I know this is not how POP3 is supposed to work, but is there a way to get dovecot to honor the user's settings in Outlook? Or should I just tell the client to turn this off and use a proper IMAP account?