How to Troubleshoot and Fix DMARC Issues

Once your DMARC record is in place, it’s not uncommon to run into problems. Emails that used to deliver fine might suddenly land in spam, some legitimate senders may fail authentication, or you might notice strange results in your reports.

DMARC brings powerful protection against spoofing, but it also demands precision. A single syntax error or misaligned domain can cause failures across your entire email system.

This guide walks through the most common DMARC issues, how to identify them, and how to fix them step by step. We also show you how DMARCeye can make that process easier and faster.

For a complete overview and roadmap of DMARC implementation, from setup to continued monitoring and beyond, see our DMARC monitoring and compliance guide.

Common DMARC Issues and How to Fix Them

Below are the six most frequent DMARC-related problems, and how to identify and fix them both manually and through DMARCeye’s dashboard.

1. SPF Failures

Symptoms:

• Your DMARC reports show “spf=fail” for known senders.
• Legitimate messages are quarantined or rejected.

Causes:

• Missing or outdated IPs in your SPF record.
• Email sent from a third-party provider (e.g., CRM, marketing platform, ticketing system) not included in SPF.
• Multiple SPF records in your DNS.

Fix:

• Use a lookup tool or a DMARC monitoring tool to see which senders are failing SPF.
• Identify if those senders are legitimate. In DMARCeye, failed IPs appear as distinct sending sources marked with red or orange status.
• If legitimate, add the sender’s include statement to your SPF record. Example
  
  v=spf1 include:_spf.google.com include:sendgrid.net -all
• After updating DNS, monitor your SPF pass rate trend to see if the issue is resolved.

Symptoms:

• DMARC reports show “dkim=fail” even for trusted senders.
• The receiving server can’t validate your DKIM signature.

Causes:

• The DKIM key wasn’t published correctly in DNS.
• You’re using the wrong selector in your configuration.
• The email service changed its DKIM settings and your DNS hasn’t been updated.

Fix:

1. Confirm that your DKIM record is live and correct. Check it using your domain and selector (e.g., selector1._domainkey.yourdomain.com).
2. Verify that the record starts with:
   
   v=DKIM1; k=rsa; p=...
3. Generate and republish a new DKIM key if the record is missing or corrupted.
4. Re-send a test message and confirm it passes DKIM validation.

3. Alignment Issues

Symptoms:

• Both SPF and DKIM pass, but DMARC still fails.
• The “header from” domain doesn’t match the domains in your SPF or DKIM records.

Causes:

• Misaligned subdomains (e.g., mailer.yourdomain.com vs. yourdomain.com).
• Third-party senders using their own domains instead of yours in headers.

Fix:

1. Review your DMARC alignment settings:
   
   aspf=r; adkim=r

2. “r” means relaxed alignment (subdomains are allowed). If you’re enforcing strict alignment (aspf=s; adkim=s), the domains must match exactly.
3. Relax alignment if you use multiple subdomains or third-party senders.
4. If you prefer strict alignment, configure each system to sign emails with your exact domain.

4. DMARC Record Syntax Errors

Symptoms:

• Reports don’t arrive.
• Testing tools show “invalid DMARC record.”
• Mailbox providers ignore your policy.

Causes:

• Missing semicolons, typos, or misformatted tags.
• Quotation marks or line breaks added by mistake.

Fix:

1. Copy your DMARC record into a validator (like dmarcian.com or MxToolbox).
2. Verify that it follows the correct format:
   
   v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com; aspf=r; adkim=r

3. Remove any unnecessary spaces or line breaks.
4. Republish and test again.

5. Missing Third-Party Authorizations

Symptoms:

• Certain services (like CRMs or newsletters) consistently fail DMARC.
• The same vendor’s IPs appear as failed sources in your reports.

Causes:

• The platform sends emails using your domain but isn’t authorized in SPF or DKIM.

Fix:

1. Check if the vendor supports custom DKIM or SPF settings.
2. Add their SPF include (if provided) to your DNS record.
3. Generate and publish a DKIM key if the platform allows it.
4. If not possible, consider using a subdomain (e.g., news.yourdomain.com) dedicated to that sender.

6. No DMARC Reports Arriving

Symptoms:

• You’ve published a DMARC record, but you aren’t receiving reports.

Causes:

• Invalid or unreachable email addresses in rua or ruf tags.
• Your receiving mailbox rejects large XML attachments.
• Providers haven’t yet started sending reports (can take up to 48 hours).

Fix:

1. Double-check your record’s reporting addresses: 
   
   rua=mailto:dmarc-aggregate@yourdomain.com; ruf=mailto:dmarc-forensic@yourdomain.com

2. Ensure those inboxes can receive attachments.
3. Use a DMARC monitoring tool to collect reports more reliably across all providers.

Using Reports to Identify and Solve Issues

Your DMARC aggregate and forensic reports are your best troubleshooting tools.

Look for patterns such as:

• Consistent SPF or DKIM failures from a single IP (likely a configuration issue).
• Unknown IP addresses sending large volumes (could indicate spoofing).
• Legitimate senders failing DKIM but passing SPF (might mean you need to check the DKIM setup for that service).

Over time, these reports will show improvements as you fix each source of failure and move toward enforcement.

How DMARCeye Helps You Troubleshoot Faster

Every DMARC record eventually needs fine-tuning, because new vendors, new subdomains, and policy changes all create potential weak spots. DMARCeye acts as your ongoing monitoring layer, ensuring that your DMARC, SPF, and DKIM setup continues to work as intended.

With DMARCeye, you can:

• Detect and fix authentication issues before they affect deliverability.
• Monitor spoofing attempts across all your domains.
• Keep a consistent, policy-compliant setup without manual XML analysis.
• Safely progress from p=none to p=reject with data-backed confidence.

Turn complex DNS troubleshooting into clear, actionable insight. 

Get a free trial of DMARCeye today and start protecting your email domain.