What Should I Do If My DMARC Reports Show Failures?

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DMARC Service


If your DMARC (Domain-based Message Authentication, Reporting, and Conformance) reports show failures, it's important to take action promptly to protect your domain from email spoofing and phishing attacks. Here’s a step-by-step guide on what you should do:

1. Understand the Cause of DMARC Failures

DMARC failures occur when emails sent from your domain do not pass the required authentication checks. DMARC relies on SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to verify the legitimacy of emails. Failure reports indicate that something went wrong in one or both of these authentication processes. The first step is to understand where and why the failure occurred.

Common reasons for DMARC failures include:

  • Missing SPF or DKIM configurations: If SPF or DKIM is not correctly set up, DMARC will not be able to authenticate the email.
  • Misconfigured DNS records: Incorrect SPF or DKIM records in the DNS can result in failures.
  • Emails sent from unauthorized servers: If an email is sent from a server that is not listed in your SPF record, it will fail the DMARC check.
  • Forwarding issues: Forwarded emails may fail DKIM or SPF checks because they often alter the message headers or the sending IP.

2. Analyze DMARC Reports

DMARC reports provide valuable insights into the emails that are failing and passing. These reports are usually sent in XML format and can be analyzed manually or with a DMARC reporting tool. Here's what you should look for in the reports:

  • Sending IP addresses: Identify which IP addresses are sending emails on your behalf. If you see an unfamiliar IP, it may be a sign of unauthorized use.
  • Authentication failures: Determine whether the failure is related to SPF, DKIM, or both.
  • Percentage of failed emails: Calculate how many emails are failing compared to the total volume of emails sent.

3. Verify SPF and DKIM Setup

If DMARC reports indicate SPF or DKIM failures, check the following:

  • SPF Record: Ensure that your SPF record in your domain’s DNS includes all IP addresses and mail servers authorized to send email on your behalf. You can use an SPF record checker to validate its configuration.

    Example SPF record:

    v=spf1 include:_spf.google.com include:servers.mydomain.com -all

  • DKIM Configuration: Verify that DKIM is properly set up on your email server. Check that your public DKIM key is published in your DNS and that the private key is correctly configured on the mail server. You can use DKIM record checking tools to verify the setup.

4. Monitor Forwarding and Third-Party Senders

One common issue with DMARC is email forwarding, which can break SPF and DKIM checks. In these cases, you may see legitimate emails flagged as DMARC failures. While you can’t control forwarding, you can adjust your DMARC policy to handle this gracefully. Setting your DMARC policy to “quarantine” or “none” will allow forwarded messages to pass, though with less strict enforcement.

Additionally, if you use third-party services (e.g., email marketing platforms, customer support tools) to send emails on your behalf, ensure they are properly configured to align with your SPF and DKIM settings. You might need to include their mail servers in your SPF record or enable DKIM for their emails.

5. Adjust DMARC Policy as Needed

Your DMARC policy determines what happens to emails that fail the authentication checks. When dealing with failures, it’s important to strike a balance between security and ensuring legitimate emails are delivered. DMARC policies include:

  • None: No action is taken, but reports are generated.
  • Quarantine: Emails that fail the check are marked as spam or placed in the recipient’s spam folder.
  • Reject: Emails that fail are outright rejected by the recipient’s server.

If you are experiencing widespread failures, start with a “none” policy to gather data without impacting email delivery. As you resolve the issues, gradually move towards a more stringent “quarantine” or “reject” policy.

6. Fix Unauthorized Sending Sources

If your DMARC reports reveal that unauthorized IP addresses are attempting to send emails from your domain, take immediate action. These unauthorized attempts may be phishing or spoofing attempts, which can harm your domain’s reputation. Steps to mitigate unauthorized sending include:

  • Block unauthorized IP addresses: Use your domain’s email security tools or firewall to block suspicious IPs.
  • Update SPF records: Remove any unnecessary or incorrect entries from your SPF record to ensure only legitimate servers are authorized.

7. Regularly Review and Update DMARC Records

Email practices and infrastructure can change over time, so it’s important to regularly review and update your SPF, DKIM, and DMARC configurations. As your organization grows, new services or servers may be introduced, requiring updates to your SPF record or DKIM setup. Stay vigilant to ensure all authorized email sources are properly accounted for.

8. Work with a DMARC Service Provider

For businesses that send a large volume of emails or rely on multiple third-party services, managing DMARC manually can become complex. DMARC service providers can automate report analysis, provide detailed insights, and help you fine-tune your authentication settings. Some of the benefits of using a DMARC service provider include:

  • Comprehensive reporting dashboards: Make it easier to spot trends and issues.
  • Automatic email authentication enforcement: Helps maintain compliance without manual updates.
  • Threat intelligence: Some services provide insights into email threats targeting your domain.

Popular DMARC service providers include:

  • Valimail
  • DMARC Analyzer
  • Agari
  • Proofpoint

9. Ensure Consistent Email Authentication Across All Domains

If your organization uses multiple domains for sending email, ensure that SPF, DKIM, and DMARC are properly configured across all domains. Even domains that are not used for sending emails should have DMARC configured with a “reject” policy to prevent attackers from using them for spoofing.

10. Educate Your Team

Finally, it’s important to educate your team about the importance of DMARC, SPF, and DKIM. This includes ensuring that all departments responsible for sending emails are aware of email authentication protocols and best practices. A well-informed team will help reduce the risk of configuration errors and improve your overall email security.

Conclusion

Dealing with DMARC failures is crucial for maintaining email security and ensuring that your emails are delivered reliably. By carefully analyzing reports, ensuring proper SPF and DKIM setup, and adjusting your DMARC policy as needed, you can reduce the risk of email spoofing and phishing attacks. Regular monitoring and updates, along with the use of a DMARC service provider, can further streamline the process and protect your domain

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