I just installed Mailvelope on Gmail using a free Chrome extension. Mailvelope is an open source PGP implementation of encryption that works easily, seamlessly, and is quite secure. It comes prefigured for Gmail, Yahoo, Outlook, and GMX. You can add others.
PGP email allows you to send encrypted email to someone who is also using PGP. Here’s how it works. If I want to send encrypted email to you, we both create a PGP key and use each others public key to encrypt to each other. Decryption is done by using your private key which only you can unlock by using your secret passphrase. This may sound complicated. However Mailvelope makes it easy and does the work for you. So do other PGP clients.
In Gmail, it adds a little icon to the email edit window. Click the icon to pop up a Mailvelope edit window. Compose your email in it. Click the padlock icon, add you it is going to. It will encrypt the message. Click transfer to copy it to the regular email edit window. Add the recipient and send
Here’s my PGP key.