Enigmail is free Thunderbird and SeaMonkey add-on that enables you to access the authentication and encryption features provided by GnuPG.
In other words, Enigmail enables Thunderbird and SeaMonkey to send and receive digitally signed and/or encrypted messages using the OpenPGP standard.
To provide the crypto-features, you must install GnuPG to. The recommended GnuPG version is 2.x since it provides gpg-agent.
Enigmail is cross-platform and it works on Mac OS X, Windows and Linux.
Detailed instructions on how to use the Enigmail add-on on your Mac are available HERE.
Here are some key features of "Enigmail":
· Encrypt/sign mail when sending, decrypt/authenticate received mail
· Support for inline-PGP (RFC 4880) and PGP/MIME (RFC 3156)
· Per-Account based encryption and signing defaults
· Per-Recipient rules for automated key selection, and enabling/disabling encryption and signing
· OpenPGP key management interface
· SeaMonkey 2.13 - 2.14 or
· Thunderbird 16.0 - 17.
What's New in This Release: [ read full changelog ]
· This is a bugfix release.
· Space dropped in passphrase with GPG key creation
· Wrong display if mail is encrypted to normal and OpenPGP-card key and card is not inserted
· Misleading OpenPGP info line shows upon clicking on pane border
· Revocation Certificate false message
· character encoding glitch
· Forwarding encrypted PGP/MIME message results in no text