If you want to be sure that your email can be read by no one but you, then it needs to be encrypted. You'd be surprised to find out who might want to read your email. I was.
One of the best encryption systems is called GPG encryption which is an open-source version of PGP encryption. PGP stand for Pretty Good Privacy and is actually an understatement made by a programmer
who didn't want to be too optimistic about how secure it is. However, as it turns out, PGP is has actually proven itself to be extremely good. It's been around for many years, being maintained by the best coders in the world and it hasn't been cracked.
In this Instructable, I'll walk you through the simple process of setting up GPG and then installing a Firefox plugin that will make it easy to encrypt your Gmail.