How do I troubleshoot DMARC reject policies and improve email deliverability?

Key findings

• DMARC reports are essential: The primary way to understand why emails are being rejected by a DMARC reject policy is to analyze your DMARC aggregate (RUA) reports. These reports provide insights into email streams, authentication results, and policy enforcement actions.
• Missing RUA address: A DMARC record with a p=reject policy and no RUA (reporting URI for aggregate reports) address means you are enforcing strict policies without any visibility into the email traffic that fails DMARC checks. This creates a blind spot.
• Domain ownership and control: DMARC is controlled by the domain owner through DNS records, not primarily by Email Service Providers (ESPs). While ESPs might assist with setup, the responsibility for the DMARC policy and report monitoring lies with the domain owner.
• Separate issues: High spam complaints are typically separate from DMARC authentication issues. While DMARC helps protect against spoofing, user complaints are usually related to content, list quality, or sending frequency. For more on this, read our guide on how to diagnose email deliverability issues.

Key considerations

• Start with p=none: Before implementing an enforcing policy (quarantine or reject), it is highly recommended to start with a p=none policy and enable reporting. This allows you to gather data on your email streams without impacting deliverability. Learn more about simple DMARC examples.
• Implement DMARC reporting: Ensure your DMARC record includes an RUA address. This directs aggregate reports (XML files) to a specified email address, which then needs to be parsed for human readability. Services like Dmarcian can help you manage and understand these reports.
• Review subdomain policies: Check if any subdomains have conflicting DMARC policies set, potentially by an ESP, which could lead to unexpected rejections. Ensure alignment across all sending domains and subdomains.
• Understand DMARC's purpose: DMARC primarily identifies whether mail comes from the domain it claims to be from, offering a layer of protection against spoofing and phishing. It provides a mechanism for domain owners to instruct receiving mail servers on how to handle emails that fail DMARC authentication.

Key opinions

• Unexpected rejections: Marketers frequently encounter situations where emails are rejected by DMARC despite proper SPF, DKIM, and good domain reputation. This indicates a deeper problem with DMARC alignment or an aggressive policy without proper monitoring.
• ESP involvement: There's a common misconception that ESPs automatically manage DMARC policies and reports. While some ESPs may offer assistance, the ultimate control and responsibility for DMARC records and report monitoring rests with the domain owner. Issues arise when ESPs configure DMARC without the sender's full understanding or access to reports, creating a blind spot.
• Importance of RUA address: Marketers are often challenged to understand the direct business impact of a missing RUA address if SPF, DKIM, and DMARC are supposedly passing. The value of RUA lies in providing crucial feedback to see if authentication is correct and if the brand is being targeted by spoofing attempts, which can affect brand trust.
• Misunderstanding DMARC's impact on reputation: Some marketers may incorrectly link DMARC itself directly to email reputation. DMARC doesn't inherently affect reputation; rather, it provides an authenticated identity upon which reputation is built. Lack of DMARC reporting (due to a missing RUA) means you're unaware of issues that could indirectly impact brand trust due to phishing.

Key considerations

• Prioritize DMARC report analysis: The first step in troubleshooting DMARC rejection issues is to gain access to and analyze DMARC reports. These reports reveal which email streams are failing authentication and why, allowing marketers to identify legitimate sources that need DMARC alignment.
• Review ESP configurations: Confirm whether your ESP has configured a DMARC record for your domain or subdomains. If they have, ensure that reporting (RUA) is enabled and that you have access to these reports. It's crucial to clarify responsibilities with your ESP regarding DMARC management.
• Transition policies carefully: Avoid jumping directly to a p=reject policy without thoroughly monitoring your email ecosystem with p=none or p=quarantine. This prevents unintended delivery failures for valid emails. Our article on how to implement DMARC p=reject safely provides a detailed approach.
• Understand DMARC reports: Since DMARC reports are in XML format, use a DMARC parsing service to make them human-readable. This is critical for gaining actionable insights into your email authentication status and identifying unauthenticated mail. You can also refer to the Mailgun blog for more insights on DMARC implementation.

Key opinions

• DMARC reports are paramount: If emails are being rejected due to DMARC, the very first step is to investigate the DMARC reports. These are the source of truth for understanding authentication failures and policy actions.
• DMARC policy ownership: DMARC is solely controlled by the domain owner through DNS records. ESPs should not be the primary managers of a client's DMARC, and if they are, it creates a potential blind spot if reporting is not transparent or accessible to the domain owner.
• Cautious policy implementation: Enforcing policies (quarantine or reject) should only be used by senders who have a clear need for them and possess the resources to actively manage DMARC reports. It's generally advised to start with p=none to avoid disrupting legitimate mail while gathering data. This is covered more extensively in our guide on safely transitioning DMARC policies.
• RUA's role: The RUA address is crucial because it's where feedback regarding authentication and potential spoofing goes. Without it, you are blind to DMARC failures and brand impersonation attempts that could indirectly affect brand trust.
• DMARC and reputation: DMARC itself does not directly impact email reputation. It's a mechanism for verifying identity, which then allows reputation to be associated with an authenticated domain. The impacts of phishing or spoofing on brand trust will occur whether or not you monitor DMARC reports, but monitoring allows you to see it coming and react.

Key considerations

• Initial policy setting: Always start DMARC deployment with a p=none policy and an RUA address. This provides data without affecting email delivery. Only transition to quarantine or reject once you are certain all legitimate mail streams are DMARC compliant. For a comprehensive overview, see our article on best practices for setting DMARC policy.
• Utilize DMARC parsers: DMARC reports are in XML format and are not human-readable. Use a dedicated DMARC parser or monitoring service to interpret these reports effectively. This is the only way to gain actionable insights into your DMARC compliance.
• Subdomain management: Be aware that some ESPs might set up DMARC policies on subdomains, potentially conflicting with your main domain's policy or creating unmonitored enforcing policies. Ensure full control and visibility over all DMARC records, particularly for subdomains. More information on DMARC policies for subdomains can be found on Email on Acid's blog.
• Separate spam complaints: Distinguish between DMARC failures and spam complaints. While DMARC protects against domain abuse, spam complaints relate to user engagement and list hygiene. Address each issue independently to improve overall deliverability.

Key findings

• DMARC's core function: DMARC allows domain owners to instruct recipient mail servers on how to handle emails that fail authentication checks, specifically concerning SPF and DKIM alignment. It's a policy layer built on existing authentication protocols.
• Policy options: DMARC offers three main policies: p=none (monitor only), p=quarantine (send to spam/junk), and p=reject (do not accept). Each policy has distinct implications for email delivery.
• Reporting is central: The DMARC specification heavily emphasizes reporting (RUA and RUF) as a critical component. These reports provide domain owners with detailed information about how their domain is being used, both legitimately and maliciously. This is essential for proper DMARC implementation, as highlighted in our guide on DMARC reports.
• Alignment requirement: For DMARC to pass, either SPF or DKIM must align with the organizational domain in the From: header. This alignment is crucial for mail to be considered legitimate by DMARC. Learn about DMARC, SPF, and DKIM in detail.

Key considerations

• Iterative deployment: DMARC deployment is a phased process, ideally starting with monitoring (p=none) to identify all legitimate sending sources before moving to enforcement policies. This prevents accidental blocking of valid emails.
• Proper DMARC record syntax: Ensure your DMARC DNS TXT record is correctly formatted and includes the rua tag with a valid email address for receiving aggregate reports. This is fundamental for receiving data. Refer to a list of DMARC tags and their meanings.
• Monitoring is continuous: DMARC is not a 'set it and forget it' solution. Ongoing monitoring of reports is necessary to detect new legitimate sending sources, identify unauthorized use of your domain, and adjust policies as your email ecosystem evolves. The DMARC RFC 7489 outlines these operational considerations.
• Subdomain handling: DMARC policies can apply to subdomains, either explicitly or through inheritance from the organizational domain. Ensure that all subdomains sending mail are properly authenticated and aligned to avoid unintended rejections under a reject policy.