Common Issues Identified In DMARC Reports And How To Resolve Them

Safeguarding your domain against email spoofing and phishing threats is crucial, and DMARC (Domain-based Message Authentication, Reporting, and Conformance) is essential for this protection. However, understanding DMARC reports can be challenging, particularly when problems occur. This guide outlines the typical issues found in DMARC reports and provides solutions to address them.

Understanding DMARC and Its Importance

DMARC is a protocol for email verification that enhances SPF and DKIM, enabling domain owners to instruct receiving servers on how to process emails that do not pass these authentication tests. Additionally, it offers reports that indicate the proper or improper use of emails, aiding in the detection of spoofing attempts, mistakes, or unauthorized senders. To effectively interpret and respond to these reports, one must have a solid understanding of their content.

1. SPF Failures

What It Means:

One frequent problem highlighted in DMARC reports is an SPF failure. This situation arises when the IP address of the sending server is absent from your domain's SPF record.

Causes:

• An additional email service has been integrated, yet it hasn't been reflected in the SPF record.
• Subdomains and marketing platforms, such as Mailchimp and Salesforce, are dispatching emails without proper SPF alignment.
• The SPF record surpasses the limit of 10 DNS lookups.

Resolution:

• Revise SPF Records: Make sure that every legitimate mail server is listed in your SPF DNS entry.
• Simplify Records: Employ SPF flattening tools or reduce the number of lookups to stay within the 10-DNS-lookup limit.
• Verify Alignment: Confirm that the domain in the “From” field corresponds with the domain checked by SPF to comply with DMARC alignment standards.

2. DKIM Failures

What It Means:

DKIM failures suggest that the digital signature of the email either failed to validate properly or did not match the domain specified in the "From" field.

Causes:

• DKIM is not activated for the email service.
• The DKIM DNS record is incorrect.
• The message was modified during transmission (which often occurs with email forwarding).
• The signature utilized a domain that does not correspond to the "From" domain, resulting in an alignment issue.

Resolution:

• Enable DKIM: Ensure your email services support and use DKIM.
• Verify Records: Double-check your DKIM DNS records are correctly published and accessible.
• Use Aligned Domains: Make sure the domain in the DKIM “d=” tag matches or aligns with the “From” domain.

3. DMARC Failures

What It Means:

A DMARC failure happens when an email fails to meet the requirements of either SPF or DKIM alignment. This indicates that the authentication details of the email do not align with the domain's specified policy, which may suggest an attempt at spoofing or phishing.

Resolution:

• Make Sure One Method is Aligned Successfully: It's best to have both SPF and DKIM set up correctly and in alignment.
• Utilize External DMARC Analysis Tools: These tools can provide insights into the points of failure and their causes.
• Gradual Enforcement Strategy: Begin with a policy of “none,” then transition to “quarantine,” and finally to “reject” as you resolve alignment problems.

4. Emails Sent from Unauthorized Sources

What It Means:

DMARC reports may reveal that there are entities sending emails using your domain without your permission.

Causes:

• Spoofing attempts by malicious actors.
• Forgotten third-party tools or marketing platforms sending legitimate emails.

Resolution:

• Identify the Source: Review IP addresses and header data to determine whether the source is legitimate.
• Whitelist Legitimate Senders: Add trusted platforms to SPF/DKIM configuration.
• Enforce Policy: Move towards “quarantine” or “reject” policies to block spoofed emails.

5. Misaligned Subdomains

What It Means:

When subdomains do not have correctly set up SPF or DKIM records, DMARC failures may happen. In the absence of these configurations, emails originating from subdomains might not pass authentication tests.

Causes:

• The subdomain is capable of sending emails, yet it adopts the DMARC policy from its parent domain without having the appropriate SPF/DKIM configurations in place.
• Subdomain records are either incorrectly configured or absent.

Resolution:

• Configure Subdomain Policies: Add specific DMARC, SPF, and DKIM records for subdomains.
• Use Wildcards Judiciously: Avoid wildcards unless absolutely necessary and ensure they don’t unintentionally allow unauthorized sources.

6. Improper DNS Record Syntax

What It Means:

Issues in the syntax of DMARC, SPF, or DKIM DNS records may lead to email delivery problems or hinder the implementation of policies.

Causes:

• Errors in DNS records due to typographical mistakes.
• Incorrect placement of semicolons, quotation marks, or whitespace.
• Surpassing character restrictions or limits on lookups.

Resolution:

Validate Records: Use online tools like MXToolbox, DMARC Analyzer, or Google Admin Toolbox to check DNS record validity.
Keep It Simple: Avoid overly complex policies or excessive DNS lookups that can cause rejection.

7. Forwarding Issue

What It Means:

Emails that are forwarded via a different mail server frequently do not pass SPF checks, and occasionally DKIM checks as well, since the servers used for forwarding usually aren’t included in your SPF record.

Causes:

• Forwarded emails seem to originate from IP addresses that are not authorized.
• DKIM signatures may be modified or removed during the forwarding process.

Resolution:

• Prioritize DKIM: Given that SPF can often break when emails are forwarded, it's important to establish a robust DKIM configuration.
• Utilize ARC (Authenticated Received Chain): Some email providers implement Authenticated Received Chain to maintain authentication even after forwarding. If possible, consider adopting this feature.

8. High Volume of Aggregate Reports

What It Means:

You are inundated with a significant number of XML DMARC aggregate reports, which complicates the manual extraction of valuable insights.

Causes:

• The domain experiences a substantial amount of email activity.
• The reports are formatted in raw XML, making them difficult to interpret without additional processing.

Resolution:

• Implement DMARC Report Parsing Tools: Utilize platforms such as Postmark, DMARCIAN, Valimail, or Agari to convert XML data into easily understandable dashboards.
• Categorize by Source: Identify the services responsible for the majority of problems and focus on addressing those issues first.

9. Policy Not Enforced (p=none)

What It Means:

The DMARC policy is configured to "none," indicating that you are observing the situation rather than taking action against messages that fail authentication.

Causes:

• A cautious implementation to collect data prior to enforcing any rules.
• Uncertainty regarding the effectiveness of your email authentication system.

Resolution:

• Gradually strengthen your policy: Transition from p=none to p=quarantine and ultimately to p=reject as your configurations become more reliable.
• Establish Reporting: Ensure you receive both aggregate (rua) and forensic (ruf) reports to analyze failures before implementing stricter measures.

Best Practices for Ongoing DMARC Success

• Consistent Oversight: DMARC requires ongoing attention; regularly checking reports is crucial to identify emerging problems.
• Evaluate Email Providers: Whenever a new email service is introduced, it must be checked against your existing SPF/DKIM/DMARC configurations.
• Record Modifications: Maintain a record of any adjustments made to SPF, DKIM, and DMARC in your change logs or IT records.
• Educate Employees: Make sure your IT and marketing personnel understand the impact of their tools on email authentication.

DMARC is one of the most powerful tools available to protect your domain from impersonation and abuse. However, merely enabling it is not enough—you must actively monitor reports, address misalignments, and fine-tune your configurations. By leveraging DMARCReport.com to proactively resolve common issues highlighted in DMARC reports, you not only safeguard your brand but also enhance email deliverability and build greater trust with your audience.