CHRISEKBLOG:

“FreeEnigma brings cryptography to webmail, with an ingenious set of free and open browser plug-ins that work with Yahoo, Gmail, and others. The plugins implement a version of GPG (the free/open version of Pretty Good Privacy) and scramble and de-scramble the text in your webmail before you send it and after you receive it, reducing the amount of information that webmail providers have on your communications. This is long overdue, as webmail and other hosted mail solutions are a ticking bomb, just waiting for a hacker, spook or copper to come a-knockin’, there to get a look at your private communications.”

“Though this is miles and miles better than the privacy that plain webmail delivers, there are a couple of ways in which this is less than perfect — the system doesn’t protect the To: and From: and Subject: information in your email; an adversary might be able to harm you just by knowing the fact that you’ve gotten encrypted mail from a specific person.”

Freenigma website

And here is a different optionI found if you’re interested.