How do I troubleshoot DMARC reject policies and improve email deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 9 Jun 2025
Updated 16 Aug 2025
7 min read
Dealing with DMARC reject policies can feel like navigating a maze, especially when your emails are authenticated, your sender reputation is high, and yet messages are still being rejected or flagged as spam. It's a common scenario that can be frustrating, impacting your email deliverability and potentially your business operations.
When Google Postmaster Tools (GPT) indicates DMARC rejections, even with good domain and IP reputation, it signals a deeper issue than just basic authentication. This often points to a misalignment or a strict DMARC policy that is inadvertently blocking legitimate mail.
Understanding why this happens and how to troubleshoot it is crucial. I'll walk you through the steps to diagnose and resolve DMARC reject policy issues, ensuring your emails reliably reach their intended inboxes.
Understanding DMARC reject policies and their impact
DMARC, or Domain-based Message Authentication, Reporting, and Conformance, is an email authentication protocol that builds upon SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). Its primary goal is to protect your domain from unauthorized use, such as phishing and spoofing.
A DMARC policy set to p=reject instructs receiving mail servers to outright reject emails that fail DMARC authentication. While this is the strongest policy for preventing fraudulent emails, it can also lead to legitimate emails being rejected if there are any misconfigurations in your SPF or DKIM records, or if there's a lack of proper alignment between your From domain and the SPF/DKIM authenticated domains.
The impact of a strict DMARC reject policy when misconfigured is straightforward: your legitimate emails won't reach the inbox. Instead, they'll bounce, resulting in lost communication, missed opportunities, and potentially a damaged sender reputation. This is why careful implementation and constant monitoring are non-negotiable.
Diagnosing DMARC failures with reports
The first step in troubleshooting DMARC reject policies is to examine your DMARC aggregate (RUA) reports. These XML-formatted reports are sent by receiving mail servers and provide crucial insights into how your domain's emails are being authenticated and handled. You can learn more about how DMARC helps troubleshoot delivery issues through Google's documentation. Without an RUA address in your DMARC record, you are essentially blind to these critical reports, which makes troubleshooting nearly impossible.
Missing RUA (aggregate report) address
If your DMARC record (as seen in a tool) doesn't specify an rua tag, you're not receiving these reports. This is a significant gap in your email security and deliverability strategy. Even if you have a p=reject policy, without reports, you cannot identify legitimate email streams that might be failing or detect unauthorized use of your domain.
DMARC reports (like those from Google and Microsoft) offer a detailed breakdown of email volume, authentication results (SPF and DKIM pass/fail), and DMARC policy application for your domain and any subdomains. Look for patterns of failures, especially for emails you know are legitimate. Common issues revealed include SPF temperror issues, DKIM signature problems, or emails sent from unauthorized sources.
Here's an example of a DMARC record that is configured for enforcement without reporting. This is a major blind spot and should be corrected immediately if you find it.
Example DMARC record with reject policy but no reportingDNS
v=DMARC1; p=reject; adkim=r; aspf=r; pct=100;
Properly configured, a DMARC record with a reporting address (like rua=mailto:reports@yourdomain.com) is crucial for visibility into your email ecosystem. If your Email Service Provider (ESP) manages your DMARC, ensure you have access to these reports or that they are being actively monitored and analyzed. Some ESPs might set up subdomain DMARC policies that conflict with your organizational domain's policy, creating unexpected rejections. It's vital to diagnose DMARC failures using these reports.
Common causes of DMARC rejection and troubleshooting steps
The spikes in delivery errors and user spam complaints in GPT, even with authenticated mail, suggest a critical issue often related to DMARC alignment. DMARC requires that the domain in the From: header (RFC5322.From) aligns with the domain authenticated by SPF (RFC5321.MailFrom/Return-Path) or DKIM (d= domain in the signature). If this alignment fails, even if SPF or DKIM technically pass, the DMARC check will fail, leading to rejection under a p=reject policy. You can find more information about DMARC policy impact on email delivery from Microsoft.
Common issues causing DMARC rejection
Subdomain conflict: An ESP might set a DMARC policy on a subdomain that conflicts with the main domain's policy, causing unexpected rejections.
Third-party senders: Emails sent through third-party services (e.g., marketing platforms, transactional email providers) must be properly configured for SPF and DKIM authentication to ensure DMARC alignment. If they don't align, even legitimate emails will be rejected.
Incorrect alignment modes: DMARC supports relaxed (r) or strict (s) alignment. If your configuration requires strict alignment, but your email setup only achieves relaxed, it could lead to failures.
The problem: DMARC p=reject misconfiguration
Implementing p=reject prematurely or without comprehensive monitoring can result in legitimate emails being blocked, leading to significant deliverability issues and disruptions in communication.
Lack of visibility: Without DMARC reports, you don't know which emails are failing and why.
Unintended blocks: Legitimate mail streams from third-party senders might not be correctly authenticated for DMARC.
Domain reputation risk: While DMARC itself doesn't directly affect reputation, the resulting delivery failures can indirectly harm it.
The solution: Phased DMARC deployment and monitoring
The safest approach is a phased DMARC implementation, starting with monitoring, then moving to quarantine, and finally to reject, while continuously analyzing reports. This allows you to implement DMARC p=reject safely.
Start with p=none: Set your DMARC policy to p=none and ensure rua is configured to receive reports. This monitors traffic without affecting delivery.
Gradual enforcement: Once confident, move to p=quarantine (sending failed emails to spam) before finally transitioning to p=reject.
The key is to proactively address any alignment issues or missing authentications identified in your DMARC reports. This includes working with third-party senders to ensure their SPF and DKIM configurations properly align with your From domain. This iterative process of monitoring, adjusting, and re-monitoring is essential for successful DMARC enforcement.
Improving email deliverability beyond DMARC
While DMARC is a powerful tool for security and plays a significant role in deliverability, it's not the only factor. High spam complaints, even with DMARC passing, indicate content-related or list hygiene issues. Receiving mail servers also consider your sender reputation, which is influenced by factors like spam complaint rates, bounce rates, and engagement.
If DMARC is correctly configured but you're still facing deliverability challenges, consider other aspects of your email program:
Content quality: Avoid spammy keywords, excessive images, or broken links that could trigger spam filters.
List hygiene: Regularly clean your email lists to remove inactive or invalid addresses, which can lead to bounces and low engagement.
Engagement: High engagement (opens, clicks, replies) signals to ISPs that your emails are valued, improving inbox placement.
By addressing these broader deliverability factors in conjunction with your DMARC configuration, you can significantly improve your email program's overall performance and ensure your messages consistently reach their intended audience, even when dealing with strict blocklist (or blacklist) policies.
Views from the trenches
Best practices
Always initiate DMARC deployment with a p=none policy to gather data and identify all legitimate sending sources before moving to stronger policies.
Regularly monitor your DMARC aggregate reports to detect potential spoofing attempts and ensure all your legitimate email streams are authenticating correctly.
Ensure that all third-party email service providers sending on your behalf are properly configured for SPF and DKIM alignment.
For subdomains used by ESPs, ensure their DMARC configuration aligns with your overall domain strategy and does not create blind spots.
Actively clean your email lists to reduce spam complaints, which can negatively impact deliverability regardless of DMARC authentication.
Common pitfalls
Setting a DMARC p=reject policy without first analyzing comprehensive DMARC reports, leading to legitimate emails being rejected.
Not configuring an RUA (aggregate report) email address in your DMARC record, leaving you blind to authentication failures and spoofing attempts.
Assuming that passing SPF and DKIM alone guarantees DMARC compliance, neglecting the crucial aspect of domain alignment.
Overlooking DMARC policies set by ESPs on subdomains, which might conflict with your primary domain's DMARC record and cause delivery issues.
Ignoring user spam complaints, which are a strong indicator of deliverability issues that DMARC alone cannot solve.
Expert tips
When dealing with a DMARC reject policy causing deliverability issues, the quickest fix is often to temporarily change the policy to p=none, then re-evaluate reports.
The primary benefit of DMARC is its reporting capability, which provides actionable intelligence to secure your domain.
If legitimate emails are being rejected due to DMARC, it's often an alignment issue with SPF or DKIM, not necessarily a reputation problem.
Reputation is associated with an authenticated identity; DMARC helps confirm that identity but does not directly impact the reputation itself.
Delegating subdomains to ESPs for DMARC configuration should be approached with caution, as it can create blind spots if reporting is not properly enabled for the domain owner.
Expert view
Expert from Email Geeks says DMARC reports are the best place to investigate if messages are being rejected due to DMARC policy.
2021-05-26 - Email Geeks
Expert view
Expert from Email Geeks says spam complaints are a separate issue and occur irrespective of email authentication status.
2021-05-26 - Email Geeks
Next steps for DMARC success
Troubleshooting DMARC reject policies and improving email deliverability requires a methodical approach. It begins with understanding that DMARC failures, even with seemingly correct SPF and DKIM, often stem from alignment issues or a lack of visibility into your email streams.
The critical step is to configure your DMARC record to receive RUA reports, interpret them, and address any authentication or alignment gaps for all sending sources. By taking a phased approach to DMARC policy enforcement and maintaining a holistic view of your sender reputation, you can resolve rejections and significantly enhance your email deliverability.
Google and 
Microsoft) offer a detailed breakdown of email volume, authentication results (SPF and DKIM pass/fail), and DMARC policy application for your domain and any subdomains. Look for patterns of failures, especially for emails you know are legitimate. Common issues revealed include SPF temperror issues, DKIM signature problems, or emails sent from unauthorized sources.
