A sudden drop in your DMARC success rate can be a perplexing issue for any email sender, signaling potential problems with email authentication or even unauthorized use of your domain. DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a protocol that builds upon SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to verify email authenticity and prevent spoofing. When your DMARC success rate declines, it means a higher percentage of your emails are failing these critical authentication checks at the recipient's server. This can lead to significant deliverability issues, with your legitimate emails potentially landing in spam folders or being rejected outright.
Key findings
Authentication changes: The most frequent cause for a DMARC success rate drop is a recent change to your SPF or DKIM records, or modifications to your email sending infrastructure that affect how these protocols are applied.
Alignment failures: Even if SPF and DKIM pass, DMARC requires that the 'From' header domain aligns with the domains authenticated by SPF or DKIM. A mismatch can cause DMARC failure.
New sending sources: Introducing a new email service provider or system that sends emails on your behalf without proper SPF or DKIM configuration will result in DMARC failures for those messages.
Spoofing attempts: An increase in unauthorized parties attempting to spoof your domain can also cause your DMARC failure rate to rise, as these emails will fail authentication.
DMARC policy impact: While a p=none policy reports failures without affecting delivery, a high volume of reported failures can still signal underlying issues that need addressing.
Key considerations
Analyze DMARC reports: The most effective way to diagnose a DMARC success rate drop is to carefully examine your DMARC reports. These reports provide detailed insights into which emails failed, why they failed (SPF, DKIM, or alignment), and the IP addresses from which they originated.
Review DNS records: Check your domain's SPF and DKIM DNS records for any recent changes or errors that might be causing authentication failures. Ensure all legitimate sending IPs are included in your SPF record.
Verify sending sources: Confirm that all services sending email on behalf of your domain are properly configured for SPF and DKIM, and that their 'From' domains align correctly. This is a common issue that causes DMARC alignment failures.
Understand policy nuances: Even with a p=none policy, some mailbox providers may still treat DMARC failures differently or use the data to inform their spam filtering decisions. For more, see this article on causes and solutions of DMARC failures.
Email marketers often face the practical challenge of managing DMARC success rates, particularly when changes occur within their email ecosystems. Their experiences highlight the immediate impact of technical configurations on deliverability and the critical role of DMARC reports in providing actionable insights. Marketers emphasize the need for vigilance and a systematic approach to troubleshooting when DMARC metrics unexpectedly drop.
Key opinions
Reports are essential: Marketers universally agree that DMARC reports are the first and most crucial place to look when success rates decline. They provide the specific 'why' behind the failures.
Configuration changes: Many marketers point to recent changes in SPF or DKIM DNS records as a common culprit for sudden drops, even if seemingly minor.
From address alignment: Issues where the 'From' address changes for parts of traffic, leading to misalignment, are frequently cited as a cause for DMARC failures.
New sending platforms: Bringing on new email sending sources or marketing tools without proper DMARC alignment can immediately impact overall success rates.
Policy interpretation: Marketers note that while p=none is for monitoring, some providers might still treat failures differently, potentially impacting delivery even without an enforcement policy.
Key considerations
Proactive monitoring: Regularly checking your DMARC reports (via Google Postmaster Tools or a DMARC monitoring tool) is critical to catch drops early.
Internal communication: Communicate with your IT department or other teams about any recent changes to email systems or sending practices that might affect DMARC authentication.
Map all sending sources: Maintain a comprehensive list of all services and IPs authorized to send mail from your domain, and ensure they are properly configured and aligned for DMARC.
Test new setups: Before fully deploying new email sending platforms or significant configuration changes, conduct thorough tests to ensure DMARC authentication and alignment remain intact. This includes checking for potential DMARC failure causes.
Marketer view
Marketer from Email Geeks suggests that the first place to investigate a DMARC success rate drop is always the DMARC reports themselves, as they are designed to shed light on why providers are failing DMARC.
10 Jun 2020 - Email Geeks
Marketer view
Email marketing manager from a marketing forum advises that monitoring DMARC reports daily is crucial to quickly detect and address any anomalies or sudden drops in authentication success rates.
15 Apr 2024 - Email Marketing Forum
What the experts say
Email deliverability experts offer a deeper, more technical perspective on DMARC success rate fluctuations. Their insights go beyond surface-level observations, delving into the intricacies of mail flow, DNS propagation, and the subtle ways in which various email systems interact with DMARC policies. Experts consistently emphasize the diagnostic power of DMARC aggregate reports and the necessity of a thorough audit of all sending infrastructure.
Key opinions
DMARC reports are definitive: Experts stress that DMARC reports provide the authoritative data needed to pinpoint the exact cause of failures, including specific IPs, domains, and authentication results.
DNS changes are critical: Any modification to SPF, DKIM, or even A/MX records can have a ripple effect on DMARC, necessitating immediate review.
Source verification: Unidentified or improperly configured third-party sending sources are a common cause of DMARC failures, highlighting the need for a comprehensive sender inventory.
Policy enforcement variations: Different mailbox providers may interpret or enforce DMARC policies, even p=none, differently, which can explain seemingly inconsistent DMARC success rates across receivers.
Subdomain impact: The use of subdomains for specific sending purposes can lead to DMARC issues if their authentication and alignment are not correctly managed.
Key considerations
Automated DMARC monitoring: Experts recommend utilizing DMARC monitoring solutions that parse and present reports in an understandable format, allowing for quick identification of failing sources and authentication issues.
Regular infrastructure audit: Conduct periodic audits of all your email sending infrastructure, including third-party platforms, to ensure consistent DMARC compliance and optimal email deliverability.
Deep dive into reports: Go beyond simple percentages. Analyze the raw DMARC aggregate XML reports (or their parsed versions) to understand specific IP addresses and sender domains causing authentication failures.
Phased DMARC deployment: For new DMARC implementations or policy changes, start with a p=none policy to gather data before moving to quarantine or rejectpolicies to avoid unintended consequences.
Expert view
Deliverability expert from Email Geeks advises that a detailed review of aggregate DMARC reports is non-negotiable for diagnosing drops, as they pinpoint the failing sources and reasons for authentication failures.
10 Jun 2020 - Email Geeks
Expert view
Industry expert from Spamresource explains that a DMARC failure indicates either unauthorized use of your domain by spammers or legitimate mail not being properly authenticated through SPF, DKIM, or both, highlighting the dual function of DMARC.
05 Jan 2023 - Spamresource
What the documentation says
Official DMARC documentation and related RFCs provide the foundational understanding necessary to diagnose and resolve issues with DMARC success rates. They lay out the precise mechanisms by which DMARC works, emphasizing the interconnectedness of SPF, DKIM, and identifier alignment. The documentation serves as the ultimate reference for interpreting DMARC reports and ensuring proper protocol implementation.
Key findings
DMARC leverages SPF and DKIM: For an email to pass DMARC, it must pass either SPF or DKIM authentication, and the domain used in the 'From' header must align with the domain authenticated by SPF or DKIM.
Identifier alignment is critical: This is a core DMARC concept, requiring the domain in the RFC5322.From header to match the domain used for SPF or DKIM validation, either exactly (strict) or by organizational domain (relaxed).
Reports for debugging: DMARC aggregate reports are the official mechanism for domain owners to receive feedback on authentication outcomes, providing data necessary to identify and troubleshoot DMARC failures.
Policy enforcement: The DMARC policy (specified by the 'p' tag) instructs receiving servers on how to handle emails that fail authentication. Even a 'p=none' policy generates reports crucial for identifying issues.
Source identification: DMARC reports help distinguish between legitimate emails failing authentication and unauthorized spoofing attempts, both of which can lower the success rate.
Key considerations
Adhere to RFC standards: Ensure your SPF, DKIM, and DMARC records are correctly formatted and published in your DNS according to their respective RFCs to avoid validation errors. For more, see the DMARC RFC 7489.
Verify SPF and DKIM setup: Before troubleshooting DMARC drops, confirm that SPF and DKIM are correctly implemented and passing for all legitimate sending domains. You can use a simple guide to DMARC, SPF, and DKIM.
Understand alignment modes: Be aware of strict versus relaxed alignment for SPF and DKIM. Relaxed alignment is more forgiving but may offer less protection against spoofing, which can subtly impact reported success rates.
Interpret DMARC tags: Familiarize yourself with the various DMARC tags in your record, such as rua (aggregate reports) and ruf (forensic reports), as they are key to effective troubleshooting. A list of DMARC tags and their meanings is a valuable resource.
Technical article
RFC 7489, the DMARC specification, outlines that DMARC success depends on an email passing either SPF or DKIM authentication, and crucially, achieving Identifier Alignment with the domain found in the 'From' header.
01 Mar 2015 - RFC 7489
Technical article
A guide from DMARC.org states that a drop in DMARC success rate frequently indicates a breakdown in either SPF or DKIM authentication, or a failure in the alignment process for a portion of the email traffic originating from a domain.
