Summary
When sending emails from a subdomain, encountering DMARC verification failures, particularly with a DMARC policy of p=reject, can lead to significant bounce rates. This issue often arises even when email service providers assure that configurations are correct. The core problem typically lies in the nuances of how DMARC, SPF, and DKIM interact with subdomains, especially concerning alignment and the absence of specific records for the subdomain itself.
Key findings
- DMARC policy inheritance: If a subdomain does not have an explicit DMARC record, it inherits the policy of the organizational (apex) domain. If the main domain has a p=reject policy, any DMARC failure on the subdomain will result in emails being rejected.
- Authentication requirements: For an email to pass DMARC, at least one of SPF or DKIM must pass and be in alignment with the From domain. If neither aligns, DMARC will fail. More details can be found on learndmarc.com.
- SPF and forwarding: SPF authentication often fails when emails are forwarded because the forwarding server's IP address is unlikely to be included in the original SPF record. This means DMARC must rely on DKIM for successful authentication.
- DKIM alignment issues: Even if an email is DKIM signed, a DMARC failure can occur if the DKIM signing domain is not aligned with the From domain, especially when sending from a subdomain that uses a different signing domain.
Key considerations
- Review DMARC reports: Analyze your DMARC aggregate reports to understand which authentication mechanism (SPF or DKIM) is failing and why, especially for your subdomain sending. This will help you troubleshoot DMARC failures.
- Verify SPF and DKIM for subdomain: Ensure that SPF and DKIM records are correctly set up and configured for your specific subdomain. While SPF records might appear fine on the apex domain, subdomain-specific issues can still arise.
- DKIM alignment: Confirm that your DKIM signature aligns with your From domain. If your emails are signed by a different domain (e.g., your ESP's domain), you might need to ensure relaxed alignment or use a CNAME for DKIM pointing back to your subdomain.
- Adjust DMARC policy for testing: Consider creating an explicit DMARC record for your subdomain with a p=none policy while troubleshooting. This will prevent rejections and allow you to gather data on authentication failures without impacting deliverability. For more on DMARC, SPF, and DKIM, consult our guide.
What email marketers say
Email marketers often face significant challenges when migrating email sending to subdomains, particularly with DMARC implementation. They frequently report receiving bounce messages indicating DMARC failures, even after their service providers claim that all configurations are correct. This discrepancy between reported setup and actual performance highlights a common frustration, leading marketers to suspect underlying issues on their end. The need for clear, actionable troubleshooting steps becomes paramount to ensure email deliverability and avoid blacklisting.
Key opinions
- Bounce message alarm: Marketers frequently identify issues through bounce messages like "Access denied, sending domain does not pass DMARC verification and has a DMARC policy of reject." These messages are direct indicators of critical deliverability problems.
- Distrust of vendor assurances: Despite partners asserting correct DMARC configuration, marketers often feel that issues persist on their side, especially with ongoing bounce messages. This highlights a need for independent verification.
- Suspected DKIM problems: Initial troubleshooting often points towards DKIM as the likely culprit for DMARC failures, even when SPF appears to be correctly set up. This indicates a common blind spot in subdomain configurations.
- Forwarding impact: While email forwarding can cause SPF failures, marketers observe that overall bounce statistics are often higher than possible forwarded messages, suggesting more widespread authentication issues.
Key considerations
- Independent verification: Marketers should not solely rely on their partners' assurances. Tools that analyze email headers can provide critical insights into SPF, DKIM, and DMARC checks, helping to troubleshoot DMARC issues.
- Focus on DKIM alignment: Given SPF's vulnerability to forwarding, ensuring DKIM is working correctly and is aligned with the From domain is often the most robust solution for DMARC passing, as highlighted by DuoCircle's guidance.
- Subdomain SPF considerations: While the main domain's SPF might be fine, creating a specific SPF record for a subdomain can sometimes resolve issues, although DKIM alignment is typically more critical for DMARC success with subdomains. More information on configuring SPF for subdomains is available.
- Temporary policy adjustment: Setting a DMARC policy of p=none for the subdomain during testing is a smart move to prevent immediate bounces while debugging, allowing for a safer warm-up process.
Marketer view
Marketer from Email Geeks explains they have added a subdomain for email sending and are encountering bounce messages during the warm-up phase. The specific error message states, "550 5.7.509. Access denied, sending domain does not pass DMARC verification and has a DMARC policy of reject" for some emails.Their partner, who configured their DMARC, claims everything is set up correctly and that the issue is not on their end. However, the marketer suspects there might be an internal configuration problem since the bounce messages persist.They also note that they do not have a specific SPF record or a separate DMARC record for the subdomain. They are seeking advice on whether creating an SPF record for the subdomain would resolve the issue or if other solutions are available.
Marketer view
Marketer from Email Geeks expresses gratitude, stating that the troubleshooting resource provided (learndmarc.com) gave them all the necessary information. This highlights the value of clear, diagnostic tools for marketers grappling with complex email authentication issues.The quick resolution after reviewing the provided resource indicates that often, the challenge for marketers is not a lack of technical capability but access to the right diagnostic information and tools to pinpoint the exact cause of DMARC failures.
What the experts say
Email deliverability experts highlight that DMARC failures on subdomains, even when SPF appears correct, frequently stem from issues with DKIM alignment or the complexities introduced by email forwarding. They stress the importance of thorough diagnostics, often recommending specific online tools and careful examination of DNS records and mail logs. Experts also advise strategic adjustments to DMARC policies for subdomains during troubleshooting to prevent unnecessary email rejections.
Key opinions
- Diagnostic tool recommendation: Experts frequently recommend using dedicated online DMARC troubleshooting tools, such as learndmarc.com, to quickly identify the root cause of authentication failures.
- Domain visibility: Sharing specific domain information helps experts analyze DNS entries and mail logs (e.g., from Comcast.net) to uncover hidden issues affecting DMARC compliance.
- SPF and forwarding: Experts confirm that SPF will not pass if messages are forwarded, making DKIM the critical authentication method for DMARC pass in such scenarios.
- DKIM alignment is key: The operational status and alignment of DKIM signatures are consistently highlighted as crucial factors for successful DMARC verification, especially when SPF is compromised by forwarding.
- Temporary DMARC policy: A valuable expert recommendation is to set a separate DMARC record for the subdomain with a p=none policy during testing phases. This prevents bounces while allowing data collection.
Key considerations
- Comprehensive diagnostic approach: When facing DMARC failures, it is essential to look beyond basic SPF checks and dive deeper into DKIM functionality and alignment. This approach helps in debugging DMARC authentication and alignment issues.
- Verify sending platform: Confirm that all emails from the subdomain originate from the expected sending system (e.g., Eloqua). This helps confirm if the correct authentication setup for that system is in place.
- Proactive DMARC configuration for subdomains: Even if the main domain has a DMARC record, explicitly configuring DMARC for subdomains, perhaps starting with a p=none policy, can provide better control and prevent unexpected rejections. For more information, explore explicit DMARC records for subdomains.
- Address forwarding issues: Be aware that SPF failures due to forwarding are common. Ensure your DMARC setup accounts for this by relying heavily on DKIM for domains that might experience forwarding, as highlighted by SendGrid in their article on addressing email delivery failures from DMARC.
Expert view
Expert from Email Geeks advises troubleshooting DMARC issues by using an online resource like learndmarc.com. This website is designed to provide comprehensive information and tools for understanding and resolving DMARC verification problems.The recommendation emphasizes a practical, self-service approach to diagnose the root cause of DMARC failures, empowering users to understand why their emails might be getting rejected even with seemingly correct configurations.
Expert view
Expert from Email Geeks suggests sharing the specific domain in question to assist with troubleshooting. Providing the domain allows other experts to examine DNS entries, such as SPF and DKIM records, and potentially check mail delivery logs for further insights.This collaborative approach highlights how community knowledge and access to domain information can expedite the diagnosis of complex deliverability issues that might not be immediately obvious to the sender.
What the documentation says
Official documentation and industry guides consistently underscore that DMARC verification failures, particularly for subdomains, are frequently attributed to incorrect SPF, DKIM, and DMARC record configurations, as well as crucial alignment issues. They advise meticulous adherence to syntax, proper DNS publication, and a phased approach to DMARC policy enforcement. Understanding how DMARC policies apply to subdomains and recognizing temporary authentication errors are also key to successful implementation.
Key findings
- Core failure reasons: DMARC failures typically result from authentication issues, domain misalignment, or general configuration errors within SPF, DKIM, and DMARC records.
- DNS record accuracy: Ensuring the DMARC record is correctly published in DNS under _dmarc.yourdomain.com and verifying its propagation and accessibility are fundamental steps.
- Subdomain policy (sp) tag: DMARC records should clearly specify the DMARC version, policy, reporting email address, and, if applicable, the subdomain policy (using the sp tag) to ensure proper enforcement across your domain hierarchy. Learn how DMARC policy application works with subdomains.
- Gradual policy enforcement: A recommended best practice is to gradually enforce DMARC policies by starting with p=none, then moving to p=quarantine, and finally to p=reject, while continuously monitoring for new rejection issues. Read our guide on safely transitioning DMARC policy.
Key considerations
- Syntax and configuration review: Carefully review DMARC record syntax and configuration for any errors. Common pitfalls include incorrect setup of SPF and DKIM, as well as misalignment between authenticated domains and the From address.
- Source verification and remediation: Documentation, such as Mailgun's guide to DMARC implementation, advises auditing sender IPs, cross-matching them with DMARC reports, and adding DMARC records to all verified sending sources.
- Adjusting from address: Some documentation suggests adjusting the From address field settings if you are using a dedicated IP, and then attempting to resend to correct DMARC failures.
- Understanding temporary errors: Be aware that DMARC TempErrors signify temporary authentication issues related to underlying email standards like DKIM and SPF, which can lead to transient DMARC validation failures. Knowing this can guide debugging efforts.
Technical article
Documentation from Mailgun advises a systematic approach to DMARC implementation, beginning with assessing existing sender IPs. This involves auditing your current sending infrastructure and cross-referencing those IPs with the data found in your DMARC reports to ensure all legitimate sources are identified.Once all verified sending sources are known, the next step is remediation. This means adding or updating DMARC records to explicitly authorize these sources, ensuring that your emails pass DMARC checks and reach their intended recipients without issues.
Technical article
Documentation from GoDMARC emphasizes the critical importance of ensuring your DMARC record is correctly published in the DNS. It must be located at _dmarc.yourdomain.com for proper detection by receiving mail servers. After publication, it is essential to verify proper DNS propagation.Verifying DNS propagation and accessibility ensures that recipient servers can find and interpret your DMARC policy, which is a foundational step in preventing DMARC failures and maintaining email deliverability.
Related resources
10 resources
Related pages
How do I set up DMARC records for subdomains?
Should I add an explicit DMARC record for subdomains?
How to configure SPF when sending from a subdomain with a different 'from' email domain?
Why is DKIM failing and how do I set it up for a subdomain?
How to troubleshoot DMARC failures and their impact on email deliverability?
Why your emails are getting a 'DMARC verification failed' error
A simple guide to DMARC, SPF, and DKIM
How to safely transition your DMARC policy to quarantine or reject
Decoding DKIM temperror: what it is and how to fix it
Demystifying the SPF TempError in your DMARC reports
