SecureGmail encrypts and decrypts the emails you send in Gmail. This happens all on your machine, and the unencrypted text never reaches Google servers. Secure Email is only as good as your password, pick an easy to guess the password and it will be easy to break. The password is decided by the user and assumes the recipient already knows it. The Secure Email plugin works only with Google Chrome. Its simple and easy to use, but at this time it works only for Chrome users.”]
Source: https://gbhackers.com/encrypt-and-password-protect-your-gmail-message-in-a-click/