http://www.rfc-editor.org/rfc/rfc7281.txt
RFC 7281: Authentication-Results Registration for S/MIME Signature Verification, A. Melnikov2014-06-01T23:00:00-00:00RFC 7001 specifies the Authentication-Results header field for conveying results of message authentication checks. This document defines a new authentication method to be used in the Authentication- Results header field for S/MIME-related signature checks.