Suppose you're truly paranoid (I assume the majority here identify with this?) and you don't want Google or other email service providers reading your email (to serve ads, etc). You don't want your ISP making backups of your messages (even with good intentions) because when you delete an email, you want it to be deleted.
One solution is to use encryption, but how many of your correspondents are sophisticated enough to use email encryption? Does Mom send you encrypted email? Probably not.
My solution is to run my own box, in my home, with a mail server that I control. Of course, the (plaintext) message could still be getting backed up somewhere: perhaps your ISP logs every packet? Or the NSA is spying on citizens again?
Question: Is my solution (home mail server) the best for my goal? Is there something better?