Summary
Receiving DMARC failure reports can be confusing, especially when your SPF and DKIM authentication records appear to be correctly configured and passing. This often indicates underlying issues that are not immediately apparent through basic authentication checks, such as email forwarding or misconfigurations in your DMARC record itself. Understanding the nuances of how DMARC works with SPF and DKIM alignment is crucial for interpreting these reports and maintaining good email deliverability. For instance, sometimes a legitimate email that successfully passes SPF authentication might still fail DMARC due to a lack of alignment or a specific forwarding scenario. This guide will help you understand why this might be happening and how to address it.
Key findings
- Email forwarding: One of the most common reasons for DMARC failures, even with correct SPF and DKIM, is when an email is forwarded. When an email is forwarded, the SPF check often fails because the forwarding server's IP address is not authorized in the original sender's SPF record. This breaks DMARC alignment.
- DKIM verification: A DMARC failure can also occur if DKIM authentication fails, for example, due to a broken DKIM entry or signature issues. Even if SPF passes, if DKIM fails and is the only mechanism DMARC relies on for that particular message, the DMARC check will fail.
- DMARC policy: A DMARC report indicating 'dmarc=none' means that no DMARC policy is published for the domain, not that a DMARC check has failed. This is an important distinction when interpreting reports. To understand more about policies, see our DMARC record and policy examples.
- Header analysis: Thoroughly examining the Authentication-Results header of the failing email can reveal the exact reason for the failure, such as which authentication method failed or if DMARC alignment was broken. This is a critical step in troubleshooting.
Key considerations
- Verify DMARC reports: Ensure the DMARC failure report genuinely indicates a failure. Sometimes reports might refer to temporary issues or indicate a 'none' policy, which isn't a failure state. Use tools to debug DMARC authentication issues.
- Address forwarding: If failures are consistently linked to specific IPs (like Microsoft's in the case of auto-forwarding), these can often be safely ignored in your DMARC analysis, as they represent legitimate forwarding traffic.
- DKIM health: Regularly check your DKIM records for integrity and proper configuration. A single broken entry can lead to significant DMARC failure rates. Review our guide on decoding DKIM temperror.
- Monitor reports: Continuously monitor your DMARC aggregate and forensic reports to identify patterns and diagnose issues promptly. These reports provide valuable insights into your email ecosystem.
What email marketers say
Email marketers often face challenges in understanding DMARC failure reports, especially when their initial checks indicate correct SPF and DKIM setup. Their experiences highlight the common pitfalls of interpreting these reports, such as confusing 'dmarc=none' with a failure, or overlooking the impact of email forwarding. The discussion among marketers often revolves around how to pinpoint the exact cause of a DMARC failure when direct authentication appears to be in order, emphasizing the need for deeper header analysis and understanding of email flow.
Key opinions
- Confusion with reports: Marketers frequently report receiving DMARC failure notices even when their own domain authentication tools show everything is fine, leading to confusion about the actual problem source. It's often difficult to identify the problem from the raw headers alone without deeper context.
- Temporary issues: There's a common assumption that a DMARC failure might be a temporary glitch or transient issue, especially if the problem is not consistently reproducible.
- Header analysis challenges: Many find it challenging to parse detailed email headers (like Authentication-Results) to identify the specific reasons for DMARC failures, such as a broken DKIM signature or SPF misalignment due to forwarding. Tools can help, but knowing what to look for is key.
- Impact of Reply-To: Some marketers incorrectly suspect that poorly formed Reply-To headers might cause DMARC failures, though this is generally not the case for DMARC authentication itself.
Key considerations
- Look beyond surface checks: Don't rely solely on basic SPF and DKIM record checks. DMARC requires alignment between the From: header and the authenticated domains. Consider how your emails are handled by intermediaries or forwarding services, as these can break alignment.
- Detailed reports: Utilize DMARC aggregate and forensic reports to gain deeper insights into the specific IPs and domains that are failing DMARC. These reports are invaluable for diagnosing subtle issues.
- Consult technical experts: If you're unsure about header interpretations or complex DMARC scenarios, seek assistance from email deliverability experts or dedicated DMARC service providers. Our guide on how to troubleshoot DMARC failures may help.
- Understand ARC: Authenticated Received Chain (ARC) can help preserve authentication results across forwarding hops, but it's not universally adopted and requires the forwarding party to implement it.
Marketer view
Email marketer from Email Geeks indicates that even with seemingly good SPF records, DMARC failures can occur, suggesting a deeper underlying issue not immediately visible. They were puzzled as to why their authentication appeared correct yet DMARC reports indicated otherwise, highlighting the complexity of email deliverability troubleshooting.
Marketer view
Email marketer from Email Geeks shared that their Return-Path domain was noreply@kiusys.com. This information is crucial for checking SPF alignment, as the Return-Path (or MailFrom) domain is used for SPF alignment against the From header.
What the experts say
Experts emphasize that while SPF and DKIM might pass individually, DMARC's unique requirement for domain alignment is often the culprit behind unexpected failures. They frequently point to email forwarding services, especially those operated by large providers like Microsoft, as a primary cause. These services often alter email headers in ways that break DMARC alignment, even if the original message was authenticated. Understanding the nuances of Authentication-Results headers is key to diagnosing these complex issues.
Key opinions
- Forwarding impact: Experts consistently identify email forwarding as a significant reason for DMARC failures, even when SPF passes. When an email is forwarded, the intermediate server typically breaks SPF alignment by sending from an IP not listed in the original sender's SPF record. This is a common challenge for legitimate mail.
- DKIM validation: Even if SPF passes, a DMARC failure can stem from a broken or invalid DKIM signature. Experts advise checking DKIM records carefully for misconfigurations, especially if the DKIM status shows a 'fail' in authentication results.
- DMARC vs. ARC: The dmarc=none status in ARC-Authentication-Results headers simply means no DMARC policy was published, not an authentication failure. Experts distinguish this from an actual DMARC fail, which occurs when SPF or DKIM alignment fails under an active DMARC policy. More on this is available in our article why DMARC fails when SPF/DKIM pass.
- Identifying source IP: Knowing the IP address from which the DMARC failure report originates, such as a Microsoft IP, can often immediately indicate a forwarding scenario. This helps determine if the failure is a legitimate concern or an expected side effect of email flow.
Key considerations
- Ignore known forwarding: If DMARC failure reports are traced to known forwarding services (e.g., Microsoft's auto-forwarding), these can often be safely ignored. These failures are typically outside the sender's control and do not necessarily indicate an issue with your domain's sending reputation.
- DNS records: Ensure your SPF and DKIM DNS records are correctly published and free of errors. Even minor misconfigurations, like extraneous SPF records or broken DKIM entries, can lead to authentication failures. Consider using a DMARC record generator tool if needed.
- Review authentication headers: Always review the full Authentication-Results header in DMARC reports. This header provides granular detail on which authentication checks passed or failed, and for what reason. For further guidance, see our article on interpreting DMARC reports.
- Adopt ARC: While not a universal fix, implementing ARC can help preserve sender authentication results through forwarding chains, allowing receiving mail servers to trust authenticated messages even after they've been modified in transit.
Expert view
Expert from Email Geeks identified an extraneous SPF record and a broken DKIM entry in the initial report, stating that this is likely why authentication is failing. This highlights that multiple misconfigurations can compound into DMARC failure.
Expert view
Expert from Email Geeks pointed out that an SPF pass combined with a DKIM fail in the ARC-Authentication-Results header suggests a DMARC pass should have occurred, but clarified that dmarc=none implies no policy, not a failure. This distinction is crucial for accurate diagnosis.
What the documentation says
Official documentation and technical standards clarify that DMARC validates email based on SPF and DKIM authentication AND alignment. Failures often occur when messages pass SPF or DKIM but the authenticated domain does not align with the From header. This is particularly relevant for email forwarding scenarios, where intermediate mail servers can break SPF alignment or modify messages in a way that invalidates DKIM signatures, even for otherwise legitimate mail.
Key findings
- DMARC alignment: DMARC requires that either the SPF-authenticated domain (the Return-Path domain) or the DKIM-signed domain aligns with the From header domain. A common reason for DMARC failure is a lack of this alignment, even if SPF or DKIM individually pass. For more on this, check out our guide to DMARC, SPF, and DKIM alignment failures.
- SPF forwarding issues: When an email is forwarded, the forwarding server acts as a new sender. This typically causes the original SPF authentication to fail because the forwarding server's IP is not included in the original sender's SPF record. This breaks SPF alignment and thus DMARC.
- DKIM modifications: Email content or header modifications during forwarding (e.g., adding disclaimers) can invalidate a DKIM signature, leading to DKIM authentication failure and subsequently DMARC failure. This is common with mailing lists or email filtering systems.
- Reporting mechanisms: DMARC provides aggregate (RUA) and forensic (RUF) reports to help domain owners monitor their email sending. These reports detail authentication results, including failures, and can help identify unauthorized sending or legitimate mail flow issues like forwarding. Learn more about DMARC tags and their meanings.
Key considerations
- Strict DMARC policies: A DMARC policy of p=reject or p=quarantine means that emails failing DMARC will be blocked or sent to spam. This can lead to legitimate emails being rejected if forwarding issues are not understood and accounted for.
- Implementing ARC: Authenticated Received Chain (ARC) is a protocol that allows intermediate mail servers to preserve email authentication results across multiple hops, helping DMARC pass even after forwarding. While not universally adopted, it's gaining traction.
- Continuous monitoring: RFC 7489, which defines DMARC, emphasizes the importance of continuous monitoring of DMARC reports. This iterative process helps identify new sending sources, detect abuse, and refine DMARC policy. DuoCircle discusses not receiving DMARC reports.
- Third-party senders: When using third-party email service providers (ESPs), ensure they properly handle SPF and DKIM alignment to your domain. This often requires specific configuration within your DNS records as per the ESP's instructions.
Technical article
RFC 7489 (DMARC) documentation states that a DMARC 'pass' requires at least one of SPF or DKIM to pass AND for the domain used for that authentication check to align with the domain in the From header. This clarifies why an individual SPF pass without alignment can still lead to a DMARC failure.
Technical article
Microsoft's email documentation explains that auto-forwarding can cause SPF to fail due to the change in the sending IP address. It recommends that senders use DKIM to maintain authentication, as DKIM is more resilient to forwarding because the signature remains intact unless the message content is altered.
Related resources
10 resources
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