Interoperability Issues between Domain-based Message Authentication, Reporting, and Conformance (DMARC) and Indirect Email Flows
Domain-based Message Authentication, Reporting, and Conformance (DMARC) introduces a mechanism for expressing domain-level policies and preferences for email message validation, disposition, and reporting. However, the DMARC mechanism enables potentially disruptive interoperability issues when messages do not flow directly from the author's administrative domain to the final Recipients. Collectively, these email flows are referred to as "indirect email flows". This document describes these interoperability issues a
Informational, not a standard. Published for the record and carrying no standards weight. Worth knowing before citing it as a requirement.
What it is
A survey of the ways indirect mail flows break DMARC, and what can and cannot be done about each.
What it solves
DMARC was deployed and legitimate mail started failing. This documents why rather than prescribing a fix.
What it means to operate
Informational, and the most useful reading on this page if you are about to move to enforcement. It is the catalogue of what will break: mailing lists, forwarding, and any service that resends on a user's behalf.
DMARC report reader shows which of your sources are indirect flows, which is the problem this document describes. Open dmarc report reader
Normative requirements
This document does not use the RFC 2119 keywords. It states its requirements in ordinary prose, which is why nothing is listed here rather than because nothing was found.