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What is the Authentication-Results header?

Authentication-Results is an email header recording authentication check outcomes. It shows whether SPF, DKIM, and DMARC passed or failed for the message, providing recipients visibility into authentication status.

Format includes: authenticating server identity, individual check results (pass/fail), and details about what was checked. Example: "spf=pass smtp.mailfrom=example.com; dkim=pass header.d=example.com; dmarc=pass".

Usage: troubleshooting authentication issues, verifying proper configuration, and understanding why messages might be filtered. Check this header when investigating deliverability problems.

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