[eluser]Rick Jolly[/eluser]
PGP is an open standard, so there are a few implemenations. Most notable are the proprietary PGP Corporation and GNUPG.
Most shared hosts have gnupg installed and you can create keys through cpanel if available. If you want a good free email client, the Mozilla Thunderbird Enigmail plugin is the best. Alternatively, you could integrate with Outlook/Express using the PGP Corporation product which is fairly full-featured even after the trial period (you just can't encrypt via the GUI after the trial, you can still decrypt).
To encrypt via php, you'll have to use the exec() or system() method and provide the correct pgp command so you'll need to know your server's path to pgp.
I've done this pgp thing a few times now. Let me know if you have specific questions or need a script example.
