The Domain Assurance Council (DAC) is creating an extension to Internet mail called "Vouch By Reference" (or "VBR" for short) that will allow certification providers to vouch for outgoing mail sent by others. VBR is based on the idea of adding an additional header to the outgoing mail, and providing a very simple way to check whether certification providers do vouch for that sender. The protocol does not require the certification provider to sign (or even know about) any mail as it is sent.
In order for a protocol to become a success in the marketplace, a variety of players need to deploy it. The following guides help various groups understand, implement, and widely deploy Vouch By Reference.
DAC has already begun interoperability testing for both VBR and DKIM (Domain Keys Identifed Mail, a standard from the IETF that works well with VBR). The tests will help DAC members be sure that the products they are deploying will work with each other, and will work well for Internet users.
