http://flossmanuals.net/basic-internet-security/ How to keep your Internet communications private
Public Key Encryption
Read through a couple of interesting guides on how you can set-up public key data encryption for your email communications.
https://flossmanuals.net/basic-internet-security/ch027_mail-encryption-gpg http://equalit.ie/esecman/chapter2_4.html#2_4b https://securityinabox.org/en/thuderbird_encryption https://www.vaultletsoft.com https://www.enlocked.com