Freenigma

Freenigma is a Firefox plugin that can encrypt your webmail. You and your correspondent both have to use Freenigma for it to work, though I think each of you can use a different webmail client. Your emails get encrypted in your own browser thanks to some JavaScript in the plugin, and so nothing gets sent to Freenigma.

This might be of use for some smaller firms in which there’s a spate of really sensitive material going to and fro in email. I doubt it’ll keep the American NSA out of things, but short of that it promises to be effective.

Freeingma is, of course, a play on free and enigma, referring to the enigma machine used by the WWII German forces, among others. Should you be interested, Wikipedia has a very thorough page on that celebrated device.