Why is DMARC failing on my .fr domain despite passing SPF and DKIM?

Mailbox providers, particularly those handling .fr domains, are increasingly strict about DMARC compliance. When your DMARC reports show no issues, yet emails are rejected, it typically points to a discrepancy between the domain used in the visible "From" header and the domains authenticated by SPF or DKIM.

Key findings

• Alignment requirement: DMARC specifically requires that either the SPF-authenticated domain or the DKIM-signed domain aligns with the RFC5322.From header domain.
• Independent passes: SPF and DKIM can technically "pass" authentication without their respective domains aligning with the "From" domain, leading to a DMARC failure. This is a common pitfall in DMARC implementation, as highlighted by eSecurity Planet.
• Subdomain impact: DMARC policies can be inherited by subdomains. If a subdomain is sending mail, its authentication must align correctly, or it needs its own explicit DMARC record.
• DNS changes: Recent changes to DNS providers or configurations can inadvertently break DMARC alignment, even if SPF and DKIM records appear to be correctly migrated.
• Aggressive policies: Implementing DMARC policies like p=reject or p=quarantine without thoroughly understanding alignment can lead to legitimate emails being blocked or sent to spam.
• Reporting limitations: Some DMARC reporting tools might show SPF/DKIM as passing without clearly indicating an alignment failure, which can be misleading.

Key considerations

• Analyze headers: Manually inspect the email headers for the Authentication-Results field to verify DMARC, SPF, and DKIM alignment status. This often reveals the true cause of failure.
• Review DMARC reports thoroughly: Look for sections in your DMARC reports that specifically indicate "non-compliant" or "non-capable" emails, as these will detail alignment failures, not just raw authentication passes. For more in-depth troubleshooting, see how to troubleshoot DMARC failures.
• Gradual policy deployment: Start with a p=none policy to monitor email flow and alignment without impacting delivery. Only move to p=quarantine or p=reject once you are confident that all legitimate mail is aligning correctly. This gradual approach is crucial for safely transitioning your DMARC policy.
• Seek expert help: If internal resources cannot diagnose the issue due to complexity or lack of data, consider consulting a DMARC specialist for a deeper investigation.

The primary issue from a marketer's perspective is the lack of clear, actionable insights when DMARC fails, especially without direct feedback or comprehensive reports from certain mailbox providers. This makes troubleshooting difficult and often requires a deeper dive into the technical nuances of DMARC alignment.

Key opinions

• Misleading passes: Many marketers are surprised when SPF and DKIM "pass" checks but DMARC still fails, indicating a gap in understanding DMARC's unique alignment requirement.
• Rejection messages: Direct rejection messages from mailbox providers (like Outlook or Apple Mail) that cite DMARC policy are critical clues, but the absence of detailed reports makes root cause analysis challenging.
• Impact of policy enforcement: Clients who prematurely implement p=reject policies without thorough monitoring often experience immediate and severe deliverability issues, impacting their email campaigns.
• DNS changes: Recent changes in DNS providers are a common trigger for unexpected DMARC failures, as existing configurations may not translate perfectly.

Key considerations

• Distinguish between pass and alignment: Marketers need to understand that SPF and DKIM simply passing doesn't guarantee DMARC alignment, which is the actual requirement for DMARC success.
• Access granular reports: Push for access to detailed DMARC reports (RUA and RUF) that show not just pass/fail, but also alignment status for SPF and DKIM, to pinpoint issues. This is crucial when considering why emails go to spam due to DMARC.
• Test thoroughly: Send test emails to various mailbox providers and analyze the raw headers to manually verify SPF, DKIM, and DMARC alignment, as explained by Kinsta.
• Adopt phased DMARC policies: Educate clients on the importance of starting with p=none and gradually moving towards stronger policies like p=quarantine or p=reject to avoid disrupting email flow. More examples can be found in our simple DMARC examples.

The consensus among experts is that abstract troubleshooting is largely ineffective. Real-world data, such as specific rejection messages from mailbox providers and detailed DMARC reports, is indispensable for accurately diagnosing these complex issues.

Key opinions

• Alignment is paramount: The core issue is almost always DMARC alignment, meaning the authenticated domain doesn't match the "From" domain.
• Data necessity: Without specific rejection messages and raw header analysis, diagnosing the problem is impossible.
• Universal alignment: DKIM and SPF alignment must be consistent across all recipient mailboxes, not just perceived by the sender or a single check.
• Subdomain considerations: DMARC policy inheritance and specific subdomain configurations must be reviewed, as subdomains can cause unique alignment challenges.
• Gradual deployment: Strongly advise against immediate p=reject without thorough monitoring at p=none.
• DMARC report interpretation: Understanding granular DMARC reports that differentiate between 'passing' and 'aligned' status is crucial for accurate diagnosis.

Key considerations

• Systematic header inspection: Routinely examine email headers for the Authentication-Results field to verify DMARC, SPF, and DKIM alignment, as this provides concrete evidence of issues.
• Leverage comprehensive DMARC reporting: Utilize DMARC reporting platforms that offer detailed views into unaligned traffic, providing the necessary data for diagnosis. This approach is key to understanding and troubleshooting DMARC reports.
• Adhere to policy phase-in: Always recommend starting with p=none and progressing cautiously to p=quarantine then p=reject, as things can break if not properly managed.
• Investigate DNS changes: Commonly, recent DNS provider changes or misconfigurations are the hidden sources of DMARC issues. For more details on common failures, see why DMARC fails despite SPF and DKIM passing.
• Consider external analysis services: If client confidentiality restricts data sharing, consider using third-party services that accept and analyze email headers to diagnose alignment issues without revealing sensitive information. This can often reveal issues that are otherwise hard to spot, as discussed by Word to the Wise.

DMARC dictates that for an email to pass its check, the domain authenticated by either SPF or DKIM must align with the domain in the RFC5322.From header (the visible sender address). This alignment can be either strict or relaxed, depending on the DMARC record's configuration, and is a key factor often overlooked when troubleshooting unexpected failures.

Key findings

• DMARC RFC definition: DMARC (RFC 7489) explicitly requires SPF or DKIM to align with the RFC5322.From domain for a DMARC pass, not just a raw pass of the individual mechanisms.
• SPF alignment: SPF alignment is achieved when the domain in the RFC5321.MailFrom (or Return-Path) matches or is a subdomain of the RFC5322.From header domain.
• DKIM alignment: DKIM alignment occurs when the domain in the 'd=' tag of the DKIM signature matches or is a subdomain of the RFC5322.From header domain.
• Strict vs. relaxed: DMARC allows for either strict (exact domain match) or relaxed (subdomain allowed) alignment, configurable via the 'adkim' and 'aspf' tags in the DMARC record.
• Aggregate reports (RUA): These XML-formatted reports provide detailed data on DMARC authentication results, including alignment status, which is crucial for identifying non-compliant sending sources. Google Support provides more information on their DMARC initiative.

Key considerations

• Understand header fields: Familiarize yourself with the relevant header fields for DMARC checks, including From:, Return-Path:, and DKIM-Signature:, and how they relate to the DMARC protocol.
• Domain comparison rules: Pay close attention to the precise domain comparison rules for SPF and DKIM alignment, as subtle mismatches can lead to DMARC failures, even if SPF or DKIM individually pass. A detailed list of DMARC tags and their meanings can be found here.
• Policy application: Remember that the DMARC policy (e.g., p=none, p=quarantine, p=reject) is applied based on the overall DMARC result, which hinges on alignment, not just individual SPF/DKIM passes.
• Utilize reporting data: Consistently review aggregate (RUA) and forensic (RUF) reports to gain comprehensive insights into authentication outcomes and pinpoint specific sources of non-compliance. See more DMARC record and policy examples here.