How can I encrypt emails sent through Gmail?

Question

What's the best solution for encrypting emails sent from within Gmail. This could be a browser extension, a GreaseMonkey script, or something else.

I realize that whoever is receiving the email will need some software configured to be able to actually read it.

Answer 1

Here is a Greasemonkey script for example: http://www.langenhoven.com/code/emailencrypt/gmailencrypt.php

Also try to google for Gmail + PGP!

Hope this helps.

Answer 2

You can configure your favorite mail client to send mail through Gmail using POP or IMAP, and use the encryption methods that are available for that client. Not sure if this is an acceptable answer on a website for web-applications though... :-) But it does increase the number of options considerably.

Answer 3

Use Gmail S/MIME.

Answer 4

There is also Penango which is a S/MIME Firefox plug-in that replaces the Gmail S/MIME plugin in Sams answer. I've been mucking around with it for a while now and it looks good, there also an IE version that i've been using as a trial, it works well.