Furthermore, I don't know of any current standard for e-mail encryption that is widely supported. No idea on how to create a key - let alone how to securely and easily exchange keys with random recipients (like a client who calls me asking me to send them some information by e-mail).
The beauty of Public Key Encryption is the public key tells the encryption software how to encrypt the measage in a way that only the owner of the public key can decrypt. To decrypt you need the private key which you should keep as a private personal secret. You can publish the public key anywhere, and exchange it any way you see fit. Slashdot either does or did at one time, an area where users can publish their public keys.
Sounds to me like your getting PKE, Public Key Encryption, confused with Kerberos an encrypted authetication protocol.