rfc-7372
Email Authentication Status Codes
This document registers code points to allow status codes to be returned to an email client to indicate that a message is being rejected or deferred specifically because of email authentication failures.
This document updates RFC 7208, since some of the code points registered replace the ones recommended for use in that document.
updates
- rfc-7208 — Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1