SecExMail makes e-mail encryption as easy as sending a message. There are no plugins necessary and it will work with any standard email client including Microsoft Outlook, Outlook Express, Calypso, Eudora and many more. Now includes automatic key exchange and powerful html filtering to protect from malicious email. Personal Edition, including support can be purchased for $4.95 using PayPal or Credit Card. Commercial and Linux versions available.
Free download