DMARC failures happen for several reasons, like DNS misconfigurations, domain alignment issues, or problems with third-party email services. These failures can lead to emails being flagged as spam, rejected, or not delivered at all, which impacts communication and security. Fixing DMARC involves proper DNS setup, aligning domains for SPF/DKIM, and authorizing third-party senders. Start with a monitoring policy, analyze reports to spot issues, and gradually enforce stricter policies to protect your domain and improve email deliverability.
Key Takeaways:
- Common Causes: DNS errors, domain misalignment, SPF lookup limits, forwarding issues, and third-party configurations.
- Fixes: Audit DNS records, ensure SPF/DKIM alignment, and monitor DMARC reports.
- Best Practice: Start with
p=none, analyze data, and gradually move top=rejectfor complete protection.
DMARC is not just about email deliverability – it’s a critical step in securing your domain and maintaining trust in your communications.
How To Fix the DMARC Fail Error
Common Causes of DMARC Failures
DMARC failures often result from configuration mistakes and technical oversights. Pinpointing these issues is essential to ensure your emails make it to the inbox.
Incorrect DNS Record Setup
A frequent culprit behind DMARC failures is human error during DNS record configuration. Even small mistakes – like omitting "v=DMARC1", missing semicolons, or misspelling tags – can cause authentication to fail.
"One small typo, and suddenly your instructions make no sense to receiving mail servers." – Valimail
Publishing multiple DMARC or SPF records for the same domain also creates conflicts, as DNS protocols can’t determine which record to prioritize. Similarly, if the DMARC record is placed on the wrong subdomain – like the root domain instead of _dmarc.example.com – mail servers won’t locate it.
SPF records, in particular, are constrained by a strict 10-lookup limit. Exceeding this limit – often due to multiple third-party services – can lead to SPF failures.
Beyond these DNS errors, domain alignment and third-party configurations present additional challenges for DMARC compliance.
Domain Alignment Problems
For DMARC to work, the domain in your "From" header must align with the domains authenticated by SPF or DKIM. Misalignment between these domains results in failed authentication. For example, strict alignment settings (like aspf=s or adkim=s) can block legitimate emails from subdomains. Additionally, if no custom DKIM signature is set up and providers use their default domains to sign emails, the DKIM signature may not match your "From" address.
Third-party services can further complicate alignment, especially when they aren’t configured correctly.
Third-Party Sender Configuration Issues
Emails sent through third-party services like CRMs, marketing platforms, or customer support tools may fail DMARC checks if these senders aren’t properly authorized in your DNS records. Many of these platforms sign outgoing emails with their own domain keys instead of your domain’s keys. For instance, a service may use a DKIM signature like d=sendgrid.net, which doesn’t align with your domain. Without adding the correct "include" statement or IP addresses to your SPF record, these emails will fail authentication.
"If you don’t configure a custom DKIM signature, email providers like Google and Microsoft will automatically sign your outgoing emails with their default DKIM key… These default signatures don’t represent your domain." – EasyDMARC
Adding multiple third-party services to a single SPF record also increases the risk of exceeding the 10-lookup limit, further complicating authentication.
Email Forwarding and Header Modifications
Forwarded emails often break DMARC alignment. When an email is forwarded, the forwarding server’s IP address typically isn’t included in your SPF record, leading to SPF failure. Additionally, if the forwarding service modifies message headers – such as by adding disclaimers or footers – the DKIM signature can become invalid, causing both DKIM and DMARC to fail.
Email Spoofing and Unauthorized Sending
Spoofed emails – where malicious actors use your domain in the "From" field – fail DMARC because they don’t pass SPF or DKIM checks. While DMARC is designed to block such fraudulent messages, its effectiveness depends on proper configuration. Without a solid DMARC policy, your domain remains vulnerable to phishing and spoofing attacks. Even parked or inactive domains are at risk. To protect unused domains, you can publish a simple DMARC record like v=DMARC1; p=reject to prevent them from being exploited.
How to Diagnose DMARC Failures
When DMARC failures occur, figuring out the root cause involves digging into reports, double-checking DNS records, and reviewing third-party sender setups.
Analyzing DMARC Reports
DMARC aggregate reports (RUA) are your go-to resource for diagnosing issues. These XML files, sent daily by major email providers, offer a detailed snapshot of your email traffic. They include data like sending IPs, authentication results, alignment status, and how each message was handled (e.g., delivered, quarantined, or rejected).
Start by establishing a baseline. Compare failure rates over the last 7 to 30 days to identify unusual spikes. Break down the data by subdomain and source IP to pinpoint problematic senders.
Key fields in the XML reports can provide valuable insights:
- Source IP: Identifies the server sending the email.
- SPF and DKIM results: Show whether the email passed technical authentication checks.
- Alignment fields (aspf/adkim): Indicate if the authenticated domain matches your "From" header.
- Disposition: Reveals the recipient’s action – no action, quarantine, or rejection.
Different failure patterns can highlight specific problems. For example:
- If both SPF and DKIM fail, it could mean an unauthorized sender or a missing configuration for a third-party service.
- If SPF fails but DKIM passes, email forwarding is likely the issue.
- If authentication passes but alignment fails, a third-party service might be using its own domain instead of yours.
Here’s a real-world example: One startup managed to cut its DMARC failures from 2.8% to 0.6% by aligning its DKIM signature with its domain.
For deeper insights, DMARC forensic reports (RUF) provide real-time details about individual failed messages, including full email headers and the "Envelope From" address. These reports are particularly helpful for investigating phishing attempts or specific failures.
Once you’ve reviewed the reports, the next step is to verify your DNS configurations.
Verifying DNS Records
DNS errors are often hidden until you actively check for them. Use tools like dig TXT _dmarc.example.com to pull your DMARC record and inspect it for common issues.
Ensure your DMARC record includes the following:
- Starts with
v=DMARC1 - Contains a valid policy tag (
p=none,p=quarantine, orp=reject) - Is published at
_dmarc.yourdomain.com
For SPF, make sure:
- Only one
v=spf1record exists at your root domain. - You haven’t exceeded the 10-DNS-lookup limit, which could trigger a "permerror" and cause DMARC failures.
Check that all DNS records for DMARC, SPF, and DKIM are properly set up. Document every DKIM selector used by third-party services and verify each one is published in your DNS.
To see how your records perform in real-time, send test emails through tools like Google Admin Toolbox’s Messageheader. This will display how SPF, DKIM, and DMARC alignment are working in practice.
Finding Third-Party Sender Problems
After analyzing reports and verifying DNS records, focus on third-party senders, as they’re often the source of alignment issues.
Start by creating a list of all external email services you use. Cross-check their IP addresses and DKIM selectors against your SPF and DNS records. Use your RUA reports to identify cases where both DKIM and SPF fail from specific IP ranges – this often points to misconfigured or unauthorized vendors.
Some vendors use their own domain for bounce handling, which can break SPF alignment.
For example, one higher-education institution improved its DMARC alignment rate from 88% to 98% by enabling DKIM signing at their campus gateway and prioritizing DKIM alignment over SPF for third-party ERP notifications.
If you’re using strict alignment settings (aspf=s or adkim=s), third-party emails sent from subdomains will fail unless they exactly match your root domain. To avoid this, consider switching to relaxed alignment (aspf=r; adkim=r) or setting up dedicated subdomains for vendors that don’t support custom DKIM.
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How to Fix DMARC Failures
Address DMARC failures by making updates to your DNS records and fine-tuning configurations.
Fixing DNS Records
Start by reviewing your DMARC record syntax:
- It should begin with
v=DMARC1and include a policy tag likep=none,p=quarantine, orp=reject. - Look for any syntax issues, such as missing semicolons, extra spaces, or multiple DMARC records.
Next, check your SPF record. Ensure there is only one record starting with v=spf1. This record should list all authorized sending IPs and include any necessary third-party include statements. Be cautious of the 10 DNS lookup limit – going over this limit will cause SPF to fail.
For DKIM, confirm that the selector (e.g., default._domainkey) matches your mail server settings and that the public key is correctly formatted. Make sure long keys are not split across multiple TXT record lines.
Finally, configure alignment modes using the aspf and adkim tags. A relaxed mode (r) allows subdomains, while strict mode (s) requires an exact match between your "From" header and authentication domains.
Adding Third-Party Senders to SPF
If you use external platforms to send emails, update your SPF record to include their specific include statements. Verify that these third-party senders meet your DKIM standards.
To protect your root domain’s reputation, consider using dedicated subdomains (e.g., marketing.yourdomain.com) for these senders. Setting aspf=r and adkim=r in your DMARC record can enable relaxed alignment for subdomains. By configuring both SPF and DKIM, you create redundancy – if one fails (e.g., SPF breaks during email forwarding), the other can still ensure a DMARC pass.
After updating your SPF record, test your changes before enforcing a stricter policy.
Testing Changes Before Enforcement
Start with a monitoring policy (p=none) to gather data without interrupting email delivery. Use the pct tag to apply the policy to a small percentage of emails (e.g., pct=10) to identify issues before a full rollout.
Once you’ve updated your DNS records, allow 24 to 48 hours for propagation. Test emails from all systems – both internal and third-party – to ensure proper DKIM signing and SPF inclusion.
Tools like Google Admin Toolbox’s Messageheader can quickly show whether SPF, DKIM, and DMARC checks passed or failed. Validators like dmarcian or MxToolbox can also help catch syntax errors before publishing your changes.
"DMARC only protects you if it’s actively monitored and enforced. Leaving it at p=none indefinitely offers no protection against spoofing." – Jack Zagorski, DMARCeye
Using Zapmail for Automated DNS Setup
Manually configuring DNS records can be tedious and prone to errors. Zapmail simplifies this process by automating the setup of SPF, DKIM, and DMARC records. It also offers pre-warmed Google and Microsoft mailboxes optimized for high deliverability, making it easier to manage bulk DNS updates, key rotations, and domain isolation without editing TXT records manually.
Zapmail ensures that your SPF records stay within the 10-lookup limit while maintaining proper alignment from the start. This is especially helpful when managing multiple domains or clients, as it scales to meet your needs while keeping each domain’s reputation isolated.
Plans start at $39/month for 10 mailboxes, providing the infrastructure and automation that would otherwise require a dedicated IT team.
DMARC Policy Enforcement Best Practices
DMARC Policy Enforcement Roadmap: From Monitoring to Full Protection
Start with Monitoring Mode (p=none)
Begin your DMARC journey with a p=none policy for 2–4 weeks. This initial monitoring phase allows you to collect DMARC reports without disrupting email delivery, giving you a comprehensive view of all legitimate sending sources across your organization’s email ecosystem.
During this period, dive into the reports daily to identify which mail streams are passing or failing. Common culprits for failures often include marketing tools, CRM platforms, and help desk systems that lack proper SPF or DKIM configuration. Surprisingly, about 75% of email senders remain stuck in this monitoring phase because they skip this crucial data-gathering step.
Once you’ve mapped out your legitimate senders, you can confidently move toward enforcement.
Move to Quarantine or Reject Policies Gradually
After reaching 95–98% DMARC compliance for all legitimate email streams, you’re ready to start enforcement. Transition gradually by implementing a p=quarantine policy at a low percentage (such as 5–10%) and slowly increasing enforcement as compliance improves.
| Rollout Phase | Policy (p=) |
Percentage (pct=) |
Purpose |
|---|---|---|---|
| Monitoring | none |
100% | Observe sender activity without affecting delivery |
| Initial Testing | quarantine |
5% to 10% | Direct a small sample of failing mail to spam |
| Partial Enforcement | quarantine |
25% to 75% | Gradually enforce as more senders become compliant |
| Full Quarantine | quarantine |
100% | Send all unauthenticated mail to spam |
| Strict Enforcement | reject |
100% | Block all unauthenticated mail completely |
Increase enforcement incrementally – moving to 25%, then 50%, and eventually 100% – while closely monitoring delivery results. Keep key teams informed before each escalation. After spending 2–3 weeks at full quarantine (p=quarantine), you can transition to p=reject to fully block spoofed or unauthenticated emails.
"Spending an extra week in quarantine mode is preferable to accidentally blocking legitimate business communications." – Red Sift
Even after reaching full enforcement, ongoing monitoring remains critical.
Monitor and Update Regularly
Once you’ve implemented p=reject, the work doesn’t stop. Weekly analysis of DMARC reports is essential to identify any new unauthorized sending sources as your organization evolves. Regularly rotate DKIM keys to maintain strong security protocols.
Additionally, audit your SPF records to ensure they stay within the 10-lookup limit and remove IPs for vendors you no longer use. Don’t forget to check subdomains – ensure they’re either covered by your main policy or have their own specific records to prevent exploitation.
"DMARC implementation requires ongoing attention as a continuous security practice rather than a one-time project." – Red Sift
The results of proper enforcement are clear. For example, Google saw a 75% reduction in unauthenticated messages after tightening bulk sender requirements in 2024. Globally, 50.2% of public companies have achieved full DMARC enforcement, and DMARC adoption grew by 11% in 2024 as organizations increasingly recognized its importance for secure email communication.
Conclusion
DMARC failures often stem from issues like incorrect DNS syntax, domain misalignment, unauthorized senders, or exceeding SPF lookup limits. These problems can weaken email deliverability, compromise brand trust, and expose security vulnerabilities.
"A DMARC fail isn’t just a technical mistake. It directly impacts deliverability, brand credibility, and security." – Valimail
To address this, start by auditing all email-sending sources and ensuring they are properly authorized in your SPF and DKIM records. Pay close attention to your DNS records – small syntax errors can disrupt email authentication across your system.
Adopt a phased approach: begin with monitoring, then move to quarantine, and finally enforce rejection once your email streams are fully compliant. Regularly reviewing DMARC reports keeps you prepared for new threats and changes to your infrastructure. By following this structured process, you can strengthen your email security and safeguard your communications.
FAQs
How can I effectively identify and resolve DMARC failures?
To fix DMARC failures, the first step is to confirm that your DMARC record is published correctly. You can use a DNS lookup tool to check for its presence. If the record is missing, you’ll need to create a basic DMARC TXT entry. Don’t forget to double-check the record’s syntax to avoid any errors or duplicates.
Next, make sure your SPF and DKIM records are properly aligned. For SPF, verify that all sending IP addresses are included in the record. For DKIM, ensure the signatures align with the domain listed in the ‘From’ field. Even if your DMARC policy is set up correctly, misalignment in SPF or DKIM can still cause issues.
Take a close look at DMARC aggregate reports to spot patterns, such as specific IP addresses or services that are triggering failures. If your emails involve forwarding or mailing lists, you might need to tweak your SPF and DKIM settings or switch to a relaxed alignment mode. Once adjustments are made, monitor these reports for at least 48 hours to track improvements and address any lingering problems. Following these steps can help restore proper email delivery and ensure your DMARC policy works as intended.
How do I set up third-party email services to comply with my DMARC policy?
To make sure third-party email services align with your DMARC policy, here’s what you need to do:
- Authorize the service in your SPF record: Update your domain’s SPF TXT record to include the third-party provider. Use their include mechanism (e.g.,
include:spf.provider.com). Remember, SPF records have a 255-character limit, and your domain should only have one SPF record. - Enable DKIM signing: Generate a DKIM key pair in the provider’s dashboard. Then, publish the public key as a DNS TXT record. Ensure the domain in the "From" address matches the signing domain for proper alignment.
- Update your DMARC record: Modify your DMARC TXT record to enforce alignment. Start with a policy of
p=noneto monitor reports. Once all senders are compliant, you can move to stricter policies likep=quarantineorp=reject. - Test and monitor: Send test emails through the service and regularly review DMARC reports to check for alignment issues. Address any problems promptly.
For a simpler process, you might want to explore tools like Zapmail. These tools can automate SPF/DKIM setup, ensure DMARC alignment, and help improve email deliverability.
How can I safely transition from a DMARC monitoring policy to full enforcement?
Transitioning from a DMARC monitoring policy (p=none) to full enforcement requires a careful, step-by-step approach to avoid disrupting email delivery. Start by enabling DMARC reports – RUA for aggregate data and RUF for forensic details. These reports help identify all sources sending emails on behalf of your domain, including third-party services and subdomains. Use this information to ensure every sender is correctly configured with SPF and DKIM. Fix issues such as missing IP addresses in SPF records or DKIM alignment problems.
Once all legitimate senders are properly set up, move to enforcement gradually. Begin by applying p=quarantine to a small percentage of emails, such as 10-20%. Monitor the reports closely to spot any new delivery failures and make adjustments as needed. Gradually increase enforcement or move to p=reject once you’re confident that all legitimate email traffic is unaffected. Throughout this process, remember to verify subdomain coverage, double-check DNS syntax, and carefully review reports after every update to ensure no legitimate senders are missed.
Tools like Zapmail can make this transition much easier by automating mailbox setup, DNS updates, and DMARC reporting, helping you achieve full enforcement without errors or unnecessary headaches.
