Re: The issue is less "encryption" and more "identity management"
The problem is you're supposed to already have the public key, not the message, because you don't know if you can trust the message. You may also want to send a message to them first, but you can't encrypt it because you don't know their public key.
Maybe putting the public key in a header is okay, if they all match from that sender then the mail client can assume it's safe to go ahead. Something like SSH's first connection certificate - it makes things easier and it's probably okay to use.
Biting the hand that feeds IT
