Why Does DMARC Fail? Troubleshooting Email Authentication Issues

Email is one of your most important communication tools, whether you’re running marketing campaigns, prospecting new clients, or supporting customers. When emails start bouncing or landing in spam, it’s more than just an annoyance. It’s a threat to your brand, your deliverability, and your business.

This article explores why DMARC fails and how to address it with clarity and confidence.

Why DMARC compliance matters

DMARC stands for Domain-based Message Authentication, Reporting and Conformance.

Mailbox providers like Gmail, Outlook, and Microsoft require DMARC to deliver your messages. Preventing DMARC from failing in Gmail or Outlook isn’t just about fixing technical issues. It’s about protecting your business at every level.

When emails consistently pass authentication, they’re more likely to land in inboxes instead of spam folders. That means higher engagement rates, better response rates, and fewer missed opportunities. If your organization relies on email for customer communication, marketing, or support, that’s a big win.

In addition, compliance helps defend your brand against spoofing and phishing attacks. When attackers try to impersonate your domain, a firm DMARC policy can stop them before they reach your customers or employees.

The role of DMARC in preventing phishing attacks

DMARC plays a decisive role in protecting your brand and customers from phishing attacks. When someone tries to spoof your domain by sending fake messages that appear to come from your business, they’re usually hoping to trick your recipients into sharing sensitive information, downloading malware, or clicking on malicious links. These attacks can be incredibly convincing, leading to lost revenue, a damaged reputation, and a breakdown in customer trust.

Without DMARC, there’s little to stop these cybercriminals from impersonating your business. However, when it is configured correctly, it acts like a gatekeeper. If someone tries to send an email using your domain without proper SPF or DKIM authentication, DMARC can tell the receiving server to reject or quarantine it. This means that the message never reaches the inbox.

This setup can be especially beneficial for industries that handle sensitive data, like finance, healthcare, or e-commerce. Customers expect their data — and inboxes — to be protected.

Why is DMARC essential for email security?

DMARC is an email security protocol that protects your domain from impersonation and works with two other authentication protocols:

• Sender Policy Framework (SPF): SPF verifies that emails come from an IP address authorized by your domain, and this can reduce fraudulent email attempts.
• DomainKeys Identified Mail (DKIM): DKIM uses a digital signature to confirm that you genuinely sent an email and that the message wasn’t tampered with in transit.

DMARC builds upon both of these core protocols. It checks whether messages pass SPF or DKIM, and whether the domains used in those checks match the domain in the email’s “From” address. Email servers with a DMARC authentication process will verify message authenticity and will result in either a “pass” or “fail.”

Why does DMARC fail?

Understanding the common reasons behind DMARC failures can help you proactively avoid or quickly resolve issues.

1. Missing or misconfigured SPF or DKIM records

If your SPF or DKIM record is missing, incomplete, or has a typo, DMARC verification will fail because mailbox providers can’t verify your messages. A forgotten IP address, an expired DKIM key, or even an extra space can break the system. This is important because even legitimate messages might get blocked or land in spam. Your team could be missing leads or invoices and not know it.

2. Domain alignment issues

Your SPF-authorized server or DKIM signature must align with your domain’s “From” address. Misalignment issues can occur when the subdomains or different domain variations are incorrectly configured. For example, if your message says it’s from “[email protected],” but the DKIM signature shows “mail.example.com,” that mismatch triggers a DMARC fail.

3. Third-party senders aren’t authenticated

Many businesses use external email services like marketing platforms, customer relationship management (CRM) systems, or transactional email providers. These third-party senders need proper authorization via SPF and DKIM records. Unless you’ve explicitly added them to your SPF record or set up DKIM with their keys, messages from these senders won’t pass DMARC.

4. Auto-forwarding and mailing list complications

Auto-forwarded emails are messages sent from [email protected] to [email protected], for example. But in this case, Bob has configured to have all emails sent to him automatically forwarded to [email protected]. As a result, SPF can fail when receiving at [email protected], even though the original message was valid. Since it passed through servers not listed in your SPF record, it will fail. In this situation, DKIM is preserved, so it might pass, but not always, especially if the forwarding server alters the message.

5. The domain is being spoofed

Sometimes, failures occur when cybercriminals try to send phishing emails using your domain. If you have DMARC in place with “p=reject,” their messages will be blocked. However, without it, those fake emails can damage your reputation.

How do you know if your emails are failing DMARC?

If you’re not sure if DMARC is the issue, there are a few key ways to check:

• Look at your DMARC reports: If your reports include “rua” or “ruf” tags, you’ll get reports from mailbox providers that show which IP addresses are sending messages using your domain and whether they passed SPF or DKIM.
• Analyze email headers: In Gmail, you can open an email, click the three dots, and choose “show original” to see whether SPF, DKIM, or DMARC failed. In Outlook, go to “View Message Details” to get this information and prevent DMARC from failing in Outlook.
• Read the bounce messages: Mailbox providers often explain why a message failed. This information can help you understand what’s going on.

How to fix DMARC failures: A step-by-step approach

With the right approach, you and your team can fix and even prevent DMARC failures.

1. Start with a monitoring policy

Set your DMARC policy to “p=none,” and the rua= and ruf= with an email address to be in charge of receiving the reports in xml format. Keep in mind that you’ll need to parse these reports — consider using a specialized DMARC monitoring tool. With a “none” policy, unauthenticated emails are not blocked. This approach offers no DMARC protection, but all the monitoring to get you started.

2. Audit all sending sources

List every tool, platform, or server that sends emails from your domain. This might include:

• Internal mail servers
• Marketing tools
• CRMs
• Transactional platforms

If any of these are missing from your SPF record or are not signing messages with a valid DKIM signature, they’ll cause DMARC failures.

3. Align your domains

Ensure the domains in your SPF and DKIM records align with your “From” address. You can start with relaxed alignment (matching subdomains is okay) and move to strict alignment later if needed.

Using SPF and DKIM together gives you stronger protection and helps ensure your messages are authenticated from multiple angles.

4. Review reports

Watch your DMARC reports and look for patterns, such as specific platforms causing repeated failures or certain IPs continuing to pop up that you don’t recognize. This insight will help you address the root issues, not just the symptoms.

5. Gradually move toward stronger enforcement

Once you’ve fixed issues and feel confident about your setup, it’s time to enforce your policy:

• “p=quarantine”: This sends messages to the spam folders.
• “p=reject”: This blocks unauthenticated emails altogether. For this step, move slowly to avoid accidentally blocking legitimate messages while tightening security over time.

Frequently asked questions

Get your pressing questions about DMARC failure answered.

1. Why did my email fail DMARC even though I set it up?

The most common reason your message might have failed DMARC is that your SPF or DKIM isn’t correctly aligned with your email’s “From” domain. DMARC only passes if at least one of those records aligns. It’s also possible that a third-party service you’re using to send emails wasn’t included in your SPF or didn’t use your DKIM signature.

2. What does “domain alignment” mean?

Domain alignment means your “From” address domain matches the domain used in your SPF or DKIM authentication. For example, if your “From” domain is example.com, but your DKIM signature shows mailservice.com, that misalignment can cause DMARC to fail. Depending on your needs, you can choose between relaxed or strict alignment settings.

3. How can I tell which service is causing DMARC to fail?

Start by checking your DMARC aggregate reports. They show which IPs or domains are sending messages using your domain and whether they passed SPF and DKIM. You can also analyze email headers manually or use tools for deeper insights.

4. How often should I review my DMARC setup?

Review it any time you add or change email services. To ensure accuracy, you can also review it at least every three to six months.

Why trust Validity to help?

DMARC failures can feel overwhelming, but with the right strategy, they’re entirely manageable. Whether fixing alignment issues, coordinating with third-party senders, or tightening your policy over time, each step brings you closer to a more secure, reliable email program.

If you’re ready to simplify the process, Validity offers trusted tools that help businesses gain complete visibility and control over their email authentication, from diagnostics to reporting and ongoing monitoring. With solutions like Validity Everest, an email deliverability platform that protects your performance, and BriteVerify, a contact validation solution that helps you build and maintain a clean and reliable database, you have all you need to take your email authentication to the next level.

Take control of your email security.

Strong email security starts with the proper support. Schedule time with our email experts to learn how we can help you protect your brand, improve deliverability, and earn the trust of every inbox you reach.