Someone in this thread made a very good point - it is hard (I'd say impossible) to create usable, mainstream E-mail encryption system based on PGP and derivatives. PGP and Web Of Trust models have fundamental limitations that prevented any meaningful adoption during the years since it was invented.

It is possible to do better with NameCoin, which promises and somewhat delivered a solution to key management and practically working robust PKI.

There is another E-mail encryption Chrome extension, called SecureDolphin (http://www.securedolphin.com) that uses NameCoin for public key delivery. Check it out in the Crome Store (https://chrome.google.com/webstore/detail/securedolphin/nefm...) if anyone is interested.