Ciphire Labs has announced Cipher Mail, a “powerful email security tool” that “requires no learning” and “works smoothly with your regular email client.”
The cross-platform software grabs your outgoing messages, retrieves the recipient’s public key, runs some security test then encrypts your message, including attachments and sends the message on its way. An explanation of the process, with an illustration of each step is available on their site if you want more detailed information.
The great thing about the software, is the fact that it works in the background with preexisting mail clients, so you can continue to use Thunderbird or Outlook (though there are many reasons to switch away from that program) in your daily routine.