The vSEC:MAIL product suite includes products that enable secure communication using email. It does this by use of industry standards for IT security such as encryption and smart cards.
Using vSEC:MAIL Server from Versasec legacy systems can transparently use S/MIME email communication. vSEC:MAIL Server supports all the most widely used email protocols (SMTP, POP3 and IMAP4). The vSEC:MAIL Server runs in a fully transparent proxy mode at a central location to generate and/or handle S/MIME secured communication. It is a proven stable and scalable .NET based solution and runs as a Windows Service. It uses X.509 certificates and private keys provided by Microsoft Windows crypto capabilities (CAPI/CNG) smart card support is also available. [pdf]
Check out the vSEC:MAIL product presentation on SlideShare
In order to understand how the vSEC:MAIL Server maybe of benefit to your organization please read the short overview document which gives a high level description of the product. [pdf]