DMARC Failure: Why Does DMARC Fail and How to Fix It?

It is concerning when your messages fail DMARC authentication, especially when your organization extensively relies on email for both internal and external communications. However, there are techniques and tools that can help you diagnose and prevent DMARC failures.

In this article, we will investigate the six scenarios that can cause DMARC failure, explain how to avoid them, and give practical advice on how to fix DMARC failures and improve deliverability.

Key Takeaways

• Alignment issues, SPF authentication problems, missing or misconfigured DKIM signatures, email forwarding, and domain spoofing attempts most commonly cause DMARC failures.
• SPF and DKIM should both be configured correctly to maximize the chances of passing DMARC, especially in forwarding scenarios.
• Third-party email providers require proper SPF and DKIM setup to send authenticated email on behalf of your domain.
• DMARC Aggregate Reports (RUA) help identify authentication issues before moving to stricter enforcement policies.
  Monitoring platforms such as DMARKOFF can simplify DMARC report analysis and help identify unauthorized sending sources faster.
• A p=reject policy provides the strongest protection against domain spoofing once all legitimate sending sources are properly authenticated.

6 Common Scenarios That Cause DMARC Failure

 

1. DMARC Alignment Failure.

 
DMARC uses domain alignment to validate emails. It checks whether the domain in the visible From address matches the domain used in SPF authentication and/or the domain in the DKIM signature. If neither SPF nor DKIM produces an aligned pass, DMARC fails.

Domain misalignment (where the SPF or DKIM domains do not match the From domain) gives the impression that an unauthorized source sent the email and is one of the most common causes of DMARC failure.

2. Strict Alignment Mode.

 
The alignment mode you select significantly affects whether messages pass or fail DMARC. For SPF alignment:

• Relaxed: SPF passes even if only the organizational domain (not the full subdomain) matches between the Return-Path and From headers.
• Strict: The domain in the Return-Path header must exactly match the domain in the From header.

For DKIM alignment:

• Relaxed: DKIM passes even without an exact match, as long as the organizational domains match.
• Strict: The domain in the DKIM signature must exactly match the domain in the From header.

Setting strict alignment in your DMARC record when your sending infrastructure uses different subdomains can cause legitimate mail to fail DMARC.

3. Missing or Incorrect DKIM Signature.

 
A missing custom DKIM signature is a frequent cause of DMARC failure. When you do not configure DKIM for your domain, your email service provider may apply a default DKIM signature that uses their domain rather than yours. This means the DKIM signature will not align with your From domain, causing DKIM alignment (and potentially DMARC) to fail. You should always configure a DKIM signature specific to your own domain on any platform that sends email on your behalf.

4. SPF Authentication Failure.

 
When configuring SPF, you must list all authorized sending sources in your domain's DNS record. Receiving mail servers perform DNS lookups to verify that the sending IP address is authorized. If a sending source is not included in your SPF record, SPF will fail for messages sent from that source.

Make sure to include all authorized third-party email service providers in your SPF record. Also note that SPF has a maximum lookup limit of 10 DNS lookups; exceeding this causes SPF to fail with a "permerror," so keep your record lean and use SPF flattening tools if necessary.

5. Email Forwarding.

 
Email forwarding routes messages through an intermediate server before delivery to the final recipient. Because the intermediate server's IP address is not listed in the original sender's SPF record, SPF typically fails during forwarding. DKIM, however, is generally preserved through forwarding unless the message body or headers are modified.

Because forwarded messages often fail SPF but can still pass DKIM, the most reliable way to ensure forwarded emails pass DMARC is to have both SPF and DKIM properly configured. An email only needs to pass one of them (with alignment) to pass DMARC. For scenarios where forwarding is common, the Authenticated Received Chain (ARC) protocol is worth considering. It preserves the original authentication results across intermediary hops and is supported by many major mail receivers.

6. Domain Spoofing.

 
When your DMARC, SPF, and DKIM configurations are all correct and legitimate mail is passing, DMARC failures can indicate that your domain is being spoofed. Bad actors attempting to send fraudulent emails that appear to come from your domain will fail DMARC authentication if you have a policy of p=quarantine or p=reject in place. In this case, DMARC failure is working as intended, it is blocking the spoofed emails from reaching recipients.

Email spoofing remains a significant and growing threat to organizational reputation. A p=reject policy provides the strongest defense against spoofing.

Why Would DMARC Fail When Sending via Third-Party Providers?

 
When using external platforms such as Gmail, Mailchimp, SendGrid, or others to send email on your behalf, you must configure DMARC, SPF, and DKIM for those providers. Failure to do so will result in DMARC failures for mail sent through those platforms.

Many teams use DMARC monitoring tools such as DMARKOFF to verify that third-party providers are authenticating correctly and to quickly identify SPF, DKIM, or alignment issues before they affect deliverability.
 

Start 14-day Free Trial

 
There are two ways to handle this:

1. Configure the authentication settings yourself through each platform's admin portal
2. Or work with the provider directly.

For Gmail, verify that _spf.google.com is included in your SPF record. For other providers like Mailchimp or SendGrid, you will typically need to add their designated SPF includes and set up custom DKIM signing using a domain alias or CNAME record pointing to the provider's signing infrastructure.

Note that as of 2025-2026, major mailbox providers (including Google, Yahoo, and Microsoft) now require bulk senders (typically those sending 5,000+ messages per day) to have DMARC, SPF, and DKIM in place or risk rejection. This is no longer optional for senders at scale.

4 Steps to Fix DMARC Failures

 

1. Start with a monitoring policy (p=none). Use DMARC Aggregate Reports (RUA) to gain visibility into who is sending email from your domain and how it is performing. This lets you identify misconfigurations and unauthorized sources without affecting mail delivery.

2. Authenticate all legitimate sending sources. Once you have mapped your sending infrastructure from the aggregate reports, ensure every legitimate source is covered by SPF (included in your DNS record) and DKIM (with a domain-aligned signature). Address any alignment issues before moving to enforcement.

3. Move to an enforced policy (p=quarantine, then p=reject). Once you are confident that all legitimate mail is authenticating correctly, move to p=quarantine to have suspicious messages sent to spam, and ultimately to p=reject to have them blocked outright. If you need to test a stricter policy before committing, the new t=y tag in RFC 9989 steps enforcement down one level (reject behaves as quarantine, quarantine behaves as none) — use this instead of the now-deprecated pct= tag for staged rollouts.

4. Analyze Failure Reports (RUF). Failure reports provide per-message details on DMARC failures, helping you pinpoint specific sources or configurations causing problems. Be aware that not all mail receivers send RUF reports due to privacy considerations, and RFC 9991 now explicitly notes that these reports may contain personally identifiable information. Handle them accordingly.

Conclusion

 
DMARC failures are not always a sign of a problem with your email infrastructure. In many cases, they highlight misconfigurations, forwarding-related authentication issues, or active spoofing attempts against your domain. By properly configuring SPF, DKIM, and DMARC, monitoring authentication results, and gradually moving toward enforcement, organizations can improve email deliverability while significantly reducing the risk of domain abuse.