PGP Encryption Proxy for Mail Server

Question

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.

Thanks!

Answer 1

If encryption is needed only until the data crosses the borders, one way would be to simply set up an off-country SMTP server, enable TLS support in it, then use it for all mail.

Advantages:

• entirely transparent to other parties;
• very easy to configure;
• no additional software or protocols are involved, just standard SMTP and TLS (SSL);
• the entire connection including message headers is encrypted (PGP only encrypts message body);
• cheap (approx. $20/mo or even less for a server, if you don't already have one – free otherwise)

Approximate process:

• obtain a server located outside the country;
• install a SMTP server (Postfix, Exim4, sendmail);
• enable connections over TLS, and possibly enable authentication;
• configure your domain name's MX records to point to the server (for incoming mail);
• configure your email program to send mail through the server.

Answer 2

There is software which will do exactly this and also provides an encrypted mailing list functionality, which is what it was originally developed for. The package is called Schleuder and its website is here:

http://schleuder2.nadir.org/

Instructions for using it as a relay between GPG users and other users are here:

http://schleuder2.nadir.org/documentation/v2.2/special_commands.html