I have a friend who is located in a part of the world that makes email encryption prudent for them. While I recommended OpenPGP, my friend thinks that it would have too high of a setup requirement for many of the people that would be sending them email. Also, they are unconcerned about the email being encrypted once it is out of the country.
So, what I was wondering is if there is a product or service available (I would prefer a reasonably priced service, but I can host it myself if need be) that would encrypt all their mail at the server using their OpenPGP public key, so everything is encrypted when they download the mail. Also, it would need to allow them to encrypt their outgoing mail, which would them be unencrypted at the email server, and continue on in plain text.