And also.. backing up his email in case he deletes his inbox/sentbox? Are you serious?
Some industries have legally mandated retention periods, both in the minimum and maximum direction.
That said, employees shouldn't have the ability to violate the corporate retention policy. You delete an email? Okay, you don't see it anymore, but it still lives on the server. You don't delete an email? Okay, but in three years, it vanishes automatically.
And yes, you can play games such as forwarding it to yourself, printing it to PDF, yadda yadda yadda, but at least on the deletion side, your admins have no excuse for not having the server automatically enforce minimum required retention times.