http://www.rfc-editor.org/rfc/rfc6651.txt
RFC 6651: Extensions to DomainKeys Identified Mail (DKIM) for Failure Reporting, M. Kucherawy2012-06-01T23:00:00-00:00This document presents extensions to the DomainKeys Identified Mail (DKIM) specification to allow for detailed reporting of message authentication failures in an on-demand fashion. [STANDARDS-TRACK]