An anti-spam protocol from the Domain Assurance Council (DAC) that enables third party certification providers to vouch for the legitimacy of the sender's domain name in an e-mail message. A Vouch By Reference (VBR) e-mail message includes the name of a trusted certification provider that the recipient queries for verification. The e-mail message is also signed via DomainKeys Identified Mail (DKIM) to verify that it has not been modified, and the signature is included in the e-mail header. See e-mail authentication. VBR-Info Header A Vouch By Reference e-mail includes a VBR-Info header that contains fields for sender's domain name, type of e-mail message and the names of one or more certification providers. For more information, visit www.domain-assurance.org.