Summary
DMARC (Domain-based Message Authentication, Reporting & Conformance) is a crucial email authentication protocol designed to protect your domain from impersonation and phishing. However, troubleshooting DMARC failures can be complex, often stemming from misconfigurations in SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) records, or incorrect DMARC policy settings. These failures can significantly impact your email deliverability, leading to legitimate emails being marked as spam or rejected entirely by recipient mail servers.
Key findings
- Policy impact: A DMARC policy set to p=quarantine or p=reject will instruct receiving mail servers to treat non-compliant emails as spam or reject them, even if legitimate, if authentication is misconfigured.
- Alignment is key: DMARC requires either SPF or DKIM to pass authentication and have their domains align with the visible From: address (RFC 5322 From). A common cause of failure is when the sending domain for SPF or DKIM does not match the From: domain, even if SPF or DKIM technically passes.
- DMARC reports: These reports provide critical insights into DMARC compliance, identifying which email streams are failing and why. Without reviewing these, it's difficult to diagnose the root cause of issues. To learn more, read about diagnosing DMARC failures using DMARC reports.
- DNS propagation: Changes to DMARC, SPF, or DKIM records can take time to propagate across DNS, meaning changes may not be immediately visible globally.
- Domain reputation: For DMARC to build and leverage domain reputation effectively, especially for your primary sending domain, both SPF and DKIM must be correctly implemented and aligned.
Key considerations
- Start with p=none: Implement DMARC with a p=none policy (reporting only) to monitor authentication failures without impacting deliverability. This allows you to identify all legitimate sending sources before enforcing stricter policies. Read more about starting with a p=none policy.
- Inspect email headers: Manually check email headers for authentication results (SPF, DKIM, DMARC pass/fail) and alignment. This can provide immediate clues to why DMARC is failing. Kinsta provides detailed guidance on how to fix DMARC fail errors.
- Ensure correct domain alignment: Verify that the domains in your SPF and DKIM authentication (the Return-Path domain for SPF, and the d= tag for DKIM) explicitly match or are a subdomain of your From: header domain.
- Review DMARC reports regularly: Use DMARC reporting services to parse the XML reports into an understandable format. This allows for continuous monitoring and identification of issues like misconfigurations or email spoofing attempts.
What email marketers say
Email marketers often encounter DMARC failures when they are not fully aware of the underlying technical requirements and the nuances of DMARC alignment. The focus is frequently on the visible impact on deliverability rather than the technical configuration details. Marketers also heavily rely on tools like Google Postmaster Tools for high-level insights, sometimes overlooking the detailed DMARC reports.
Key opinions
- Deliverability impact: Many marketers experience emails landing in the junk folder, particularly with Microsoft, and observe unpredictable or low open rates.
- Google Postmaster dependency: Marketers frequently state that if Google Postmaster Tools reports no DMARC issues, then there is no problem, sometimes disregarding other diagnostic methods. Learn more about Google Postmaster Tools.
- Header inspection importance: Checking individual email headers is recommended to pinpoint authentication results for SPF, DKIM, and DMARC.
- Domain reputation goals: Marketers aim to send emails from their primary brand domain to leverage its existing reputation, often unaware of the technical alignment needed for DMARC to support this.
- Confusion with policy changes: Changes to DMARC policies, such as moving from p=quarantine to p=none, can initially cause confusion about their impact on email deliverability.
Key considerations
- Consistent sender domain: Ensure that the email address used in the From: header (visible to recipients) matches the domain or a subdomain authenticated by SPF or DKIM for DMARC to pass.
- Review DMARC reports: Marketers should gain access to and understand DMARC aggregate and forensic reports to proactively identify and resolve authentication issues, rather than solely relying on Postmaster Tools.
- Implement DKIM: DKIM is a prerequisite for building domain reputation. Implementing DKIM signing for all legitimate email streams from your primary domain is crucial for DMARC success and improved deliverability. Read how to verify SPF, DKIM, and DMARC.
- Coordination with IT/CTO: Close collaboration with technical teams (CTO, IT) is essential to ensure DMARC, SPF, and DKIM configurations are correct and aligned with marketing sending practices.
- Address all sending sources: Identify and properly authenticate all legitimate email sending platforms, including marketing automation tools and transactional email services, to prevent DMARC failures.
Marketer view
An email marketer from Email Geeks suggests that marketers send themselves messages from all platforms they are responsible for and then check the email headers. This practice helps verify the actual authentication results.
Marketer view
A marketing professional from Email Geeks advises that if email headers show no issues, then the problem might not exist, but it's still crucial to check DMARC reports for signs of large-scale spoofing.
What the experts say
Email deliverability experts highlight that DMARC implementation is highly specialized and requires a deep understanding of email authentication protocols like SPF and DKIM, particularly concerning domain alignment. They emphasize that simply publishing a DMARC record without proper configuration and monitoring can inadvertently harm deliverability by telling mailbox providers to reject or quarantine legitimate emails. Experts often advise a cautious approach, starting with a p=none policy and utilizing dedicated reporting tools.
Key opinions
- DMARC logic: DMARC passes if an email passes either SPF OR DKIM, provided the identifiers align with the From: header domain.
- Incompatible authentication: If SPF and DKIM authentication domains do not align with the From: header, DMARC will always fail, regardless of SPF or DKIM passing. This is a common reason for DMARC verification failure.
- DMARC policy impact: Setting a DMARC policy to p=quarantine or p=reject with authentication issues can lead to legitimate emails being sent to spam or discarded by mailbox providers.
- Importance of reports: The primary value of DMARC lies in its reporting capabilities, which reveal poorly authenticated email streams. Without analyzing these reports, implementing a DMARC policy (beyond p=none) offers little benefit.
- Complexity of DMARC: DMARC is a highly specialized protocol, and improper implementation can easily break email deliverability, especially when trying to enforce policies without full authentication coverage. See a simple guide to DMARC, SPF, and DKIM.
Key considerations
- Correct domain alignment: The domain used for SPF (smtp.mailfrom) or DKIM (d=) must match the From: header domain for DMARC to pass. This is often the fundamental issue in DMARC failures. Learn about troubleshooting SPF and DMARC settings.
- DMARC policy adjustments: If DMARC is consistently failing, the policy should be set to p=none to avoid legitimate emails being rejected or sent to spam until all email streams are properly authenticated and aligned. For more details, refer to the Email on Acid blog.
- Comprehensive authentication: Ensure all email sending sources are identified and correctly configured with SPF and DKIM, using the domain intended for DMARC alignment.
- Understanding Precedence: bulk: This header is appropriate for bulk mail and signals to recipients not to send automatic replies. It does not cause DMARC failures. Find out what RFC 5322 says versus what actually works.
- Continuous monitoring: Regularly review DMARC reports and adjust configurations as needed, especially when new sending platforms are introduced or existing ones are modified.
Expert view
An email expert from Email Geeks explains that DMARC is typically configured with an OR logic. This means DMARC passes if an email successfully authenticates with either SPF or DKIM, provided the identifiers (domains) are aligned.
Expert view
An email expert from Word to the Wise states that DMARC authenticates the visible 'From' address, which is the RFC 5322 From header. This is the domain that must align with SPF or DKIM for DMARC to pass.
What the documentation says
Technical documentation on DMARC, SPF, and DKIM consistently emphasizes the importance of domain alignment between the From: header and the authenticated domains. It provides specific instructions for configuring these records and troubleshooting common issues. Documentation often highlights that DMARC policies, such as p=quarantine or p=none, directly influence how recipient servers handle emails that fail DMARC checks. For a deeper dive, check out our list of DMARC tags and their meanings.
Key findings
- Authentication standards: DMARC leverages SPF and DKIM for email authentication, requiring at least one to pass and align with the From: header. For more info, read our DMARC record and policy examples.
- Policy definitions: The p= tag in a DMARC record defines the policy for emails that fail authentication. Common policies include p=none (monitor), p=quarantine (send to spam), and p=reject (block).
- Percentage tag (pct=): This tag specifies the percentage of emails to which the DMARC policy should be applied, allowing for gradual policy enforcement. If not set, it defaults to 100%.
- DKIM setup: Platforms like SmarterMail provide specific knowledge base articles on how to create and set up DKIM records to ensure email signing.
Key considerations
- Strict vs. relaxed alignment: The aspf and adkim tags control DMARC alignment mode (strict or relaxed), impacting how exact the domain match needs to be.
- DMARC record syntax: Adhering to the correct DMARC record syntax, including policy (p=) and reporting (rua, ruf) tags, is crucial for proper DMARC functionality.
- DKIM i= and d= fields: Understanding how these fields relate to the signing domain and the 'From' header is vital for correct DKIM and DMARC alignment. Learn to troubleshoot DKIM failures.
- Email forwarding: Technical documentation often highlights that email forwarding can break SPF alignment, leading to DMARC failures, and may require DKIM alignment to pass. Read how to handle DMARC failures when email is forwarded.
Technical article
SmarterTools documentation provides a guide on how to create a DKIM record within their SmarterMail platform, outlining the necessary steps for proper email authentication.
Technical article
SmarterTools documentation offers detailed instructions for setting up email signing with DKIM, ensuring that emails sent through their platform are correctly authenticated.
Related resources
15 resources
Related pages
Why does DMARC authentication fail when SPF and DKIM pass, and how can it be fixed?
How do I troubleshoot and fix SPF and DMARC settings for email deliverability issues?
How can I troubleshoot DMARC failures and identify the cause of authentication issues?
How to handle DMARC failures when email is forwarded by recipients?
How to diagnose DMARC failures using DMARC reports?
List of DMARC tags and their meanings
Simple DMARC examples: how to start with a p=none policy
A simple guide to DMARC, SPF, and DKIM
Why your emails are getting a 'DMARC verification failed' error
How to safely transition your DMARC policy to quarantine or reject
