Enigmail - A simple interface for OpenPGP email security

Enigmail is a security extension to Mozilla Thunderbird and Seamonkey. It enables you to write and receive email messages signed and/or encrypted with the OpenPGP standard. Sending and receiving encrypted and digitally signed email is simple using Enigmail. It supports powerful GUI for easy configuration and OpenPGP key management, Integrated OpenPGP PhotoID viewer and lot more.