Resources
Guides to email authentication, with links to the original standards.
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Understanding DMARC
What DMARC does, how SPF and DKIM fit in, and why alignment matters.
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DMARC deployment checklist
Publish a DMARC record, review reports, and move to enforcement.
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Troubleshooting DMARC failures
Work from a real message to the authentication or alignment problem behind it.
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How to choose a DMARC provider
The questions to ask about reporting, support, limits, and your route to enforcement.
Reference material
DMARC protocol — RFC 9989
The current Standards Track specification for DMARC, published in May 2026.
Aggregate reporting — RFC 9990
The DMARC aggregate report format and reporting behaviour.
Failure reporting — RFC 9991
The specification for message-specific DMARC failure reports.
SPF — RFC 7208
How SPF authorises sending hosts for a domain.
DKIM — RFC 6376
The base specification for domain signatures on email.
Gmail sender guidelines
Google’s requirements for mail sent to personal Gmail accounts.
Yahoo sender best practices
Yahoo’s authentication, unsubscribe, and sending requirements.
DMARC.org
Protocol background, specifications, and DMARC community updates.