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.
What it is
Assigns enhanced status codes for authentication failures, so a rejection can say it was DMARC rather than something generic.
What it solves
A message refused for policy reasons came back as an ordinary 5.7.1, indistinguishable from any other block.
What it means to operate
5.7.26 means the message failed multiple authentication mechanisms. It is a configuration problem, not a reputation one, and retrying will never clear it.
Bounce classifier turns one of these status codes into the action it calls for. Open bounce classifier
Normative requirements
Every sentence in this RFC carrying an RFC 2119 keyword, with the section it came from.
4 General Considerations
- SHOULDIf a receiving server performs multiple authentication checks and more than one of them fails, thus warranting rejection of the message, the SMTP server SHOULD use the code that indicates multiple methods failed rather than only reporting the first one that failed.