A long time ago, in a galaxy not too far away, I took part in a JISC funded research project. The purpose of the project was to investigate and develop solutions for some of the issues associated with securing email.
It was a fun project to be involved with (not least because I got to pretend to be a student again for a little while), and I believe the solution we built – the Secure Email Proxy – was a good one with a lot of potential.
The project finished in 2003, and the website (hosted on an old Sun Pizza box in my lab) has long since vanished, along with the code for the project. I think this is a shame, so I’ve stuck my old development code up on Github. The proxy was under active development since I left the project, but I’ve not go access to the code. If you do, then please feel free to fork and update it.
Anyway, the proxy works by sitting on your local machine between your mail client and your mail server. It manages keys on your behalf, and encrypts/signs/verifies/decrypts messages and attachments on the fly as email passes through it. This means that you don’t need to have any native plugin to work, and it’ll work with virtually any mail client.