What is a DMARC Fail?

A DMARC fail happens when a message does not pass SPF or DKIM tests that are used to check the envelope and header information respectively and further does not match the domain stated in the ‘From’ field according to the DMARC policy, resulting in either rejection or quarantining of the email based on the policy in use.

Reasons for DMARC Failure

A DMARC failure can occur for several reasons, often related to issues with email authentication, domain alignment, or incorrect configurations. Here are the common reasons why a DMARC failure might occur:

SPF Failure

• SPF Record Not Configured Correctly: If the SPF record of the sending domain does not exist or is not properly set up or if the sending server’s IP address is not authenticated in the record, then the email fails the SPF check.
• SPF Record Too Permissive: If the SPF record is too relaxed (for example, if it reads +all), it implies that other third-party servers can send emails on the domain’s behalf, resulting in DMARC failure.
• Too Many DNS Lookups: The retrieve rate of SPF records has been restricted to 10 DNS lookups. If exceeded, the check made by SPF will fail, and this leads to a possible DMARC failure.

DKIM Failure

• Missing or Incorrect DKIM Signature: If the message does not have a DKIM signature or an incorrect one, then the email does not pass through DKIM authentication.
• Key Misalignment: If the DKIM key used to sign the email is not the one that was published in DNS for the domain of origination, then DKIM fails.
• Expired DKIM Key: If the DKIM key stored in the DNS has expired or been revoked, then authentication based on it will fail and result in a DMARC fail.

Domain Alignment Issues

• SPF or DKIM Misalignment: DMARC enhances SPF or DKIM by mandating that the email domain matches the “From” domain. If there is a mismatch, the DMARC check should fail in the email.
• Subdomain vs. Root Domain: Sometimes, while sending an email, the username that appears in the ‘From’ header uses a subdomain that does not conform to the DMARC policy of the root domain and, hence, leads to a failure.

Improper DMARC Policy Configuration

• Inconsistent Policies Across Domains: If you have multiple domains and subdomains, having different or even conflicting DMARC policies, this may result in legitimate emails failing DMARC.
• Aggressive DMARC Policy: When the DMARC policy is set as quarantine or rejected, without proper testing exercises, legitimate Internet messages may fail DMARC due to false positives.

Forwarding Issues

• Email Forwarding: Whenever mails are being forwarded, the original SPF and DKIM signatures may not be passed through the forwarding server, hence resulting in a DMARC fail.
• Mailing Lists: Emails sent through mailing lists are usually changed, affecting the signature’s integrity and thus making DMARC fail.

Third-Party Email Services

• Unauthorized Third-Party Senders: Lack of authentication (for instance, your SPF or DKIM does not include third-party services through which you send emails on your behalf, e.g., marketing platforms) will make those emails fail DMARC.
• Multiple Third-Party Providers: If you use several third-party providers, it can cause DMARC failures due to improper setup or even inconsistency in how these providers manage the authentication procedures.

Missing or Incorrect DNS Records

• Missing DMARC Record: If the DMARC record is not published or is incorrect, DMARC checks are not possible and thus can fail.
• DNS Propagation Delays: When analyzing the SPF, DKIM, or DMARC records, it might take some time before the changes take root due to propagation delays, which may lead to what is referred to as DMARC fails.

How to Know if You Had a DMARC Failure Happened?

Detecting a DMARC failure is crucial to understanding whether your emails pass the necessary authentication checks. Here’s how you can determine if a DMARC failure has occurred:

Check DMARC Reports
DMARC offers two kinds of reports; these are RUA or aggregate reports and RUF or forensic reports that can be used to assess the effectiveness of your email authentication and, conclusively, the inefficiencies as well.

SPF/DKIM reports are XML-based summaries that provide the combined set of SPF and DKIM checks on the overall emails sent from the domain. These reports are delivered by receiving email servers to the email address stated in the rua tag of your DMARC record.

From these reports, you can learn whether your emails have been passing or failing DMARC checks and whether the recipient servers that handled the emails acted upon them or not, which is either by sending them to the destination folder, quarantining them, or even rejecting them outright.

If your DMARC fails, the forensic reports show the specific failed emails, including details in the email headers as to why the failure occurred.

It is practical to review such reports often to ensure the safety of your domain’s email and, in case of DMARC failures, to rectify them on time.

Monitor Email Bounce Messages
The other method of identifying DMARC failures is to look for bouncers or emails that have been rejected by the mail server.

If an email does not pass DMARC checks and your policy is set to either quarantine or reject, then the recipient server may not deliver the email, and it gets returned to the sender.

This bounce message often consists of error codes and messages showing why the particular email was not delivered.

These error messages also contain valuable information about problems that occurred due to SPF, DKIM, or DMARC policies and can help in their diagnosis.

If we listen to these Bounce Messages, one can quickly resolve any DMARC failures that could lead to blocking some genuine emails or marking them as spam.

Email Logs and Analytics
If you operate your email server, the server logs will be quite a valuable tool to identify the DMARC failures.

This means that the server logs contain detailed records of every single email transaction including the results of the checks of SPF, DKIM AND DMARC.

Analyzing these logs, you will see the cases of emails that were checked by DMARC and quarantined or rejected further.

Third-party email analytics tools available online, including Postmark and SendGrid, can also assist you in identifying delivery problems, including DMARC failings.

Such tools typically come equipped with dashboards and reports showing you which authentications have gone wrong, and you can correct the situation.

User Complaints or Feedback
Sometimes, these first signs of a DMARC failure emanate from the recipients of your emails without your knowledge.

If your emails are bouncing or are not reaching users’ inboxes but being filtered into the spam folder, then these could be some DMARC failed checks.

The recipients might state that they never saw the message that you sent them or that your message ended up in the spam folder.

This could signal that something is wrong with your email authentication settings, which will compel you to investigate.

Use Online DMARC Check Tools
The use of online monitoring services as well as tools will help one to find out if their domain is affected by DMARC failures. These tools enable you to type in your domain name and check a DMARC policy to know how it is faring.

They frequently deliver the digest of the current email authentication situation in your domain with the list of failed scenarios and problems that occurred.

Performing these tools routinely shall assist you in monitoring the protection of the domain and that of the mail adequately authenticated.

Configure Alerts in Your Email System
Most of the email systems and DMARC monitoring services provide the features of configuring notifications that would inform you about the occurrence of DMARC failures.

They can be set up to notify a specific moment in which many of your emails fail DMARC checks, so it is easy to address the problem.

By creating these alerts, you will receive notifications that help you know if an email authentication has failed, and the emails won’t go unnoticed.

Domain Monitoring
Such failures are best detected in real-time by constantly tracking your domain’s email authentication status.

Temperature checks are essential when it comes to the assessment of the DMARC policy itself and possible failures that may arise in the future — with the help of constant monitoring; the changes will be easily spotted.

This approach is advantageous as it prevents problems from arising in the first place so that mail can be delivered effectively and safely.

How to Fix a DMARC Fail Error?

Despite your hard work configuring the email authentication protocols, DMARC (Domain-based Message Authentication, Reporting, and Conformance) failures may arise.

These failures are usually a result of misconfiguration or things that go wrong with handling emails for your domain by mail servers.

However, if the errors are tackled and organized, one can quickly correct them on the construction floor. Below are three significant steps that will help one correct the DMARC fail error:

Set up SPF and DKIM authentication for DMARC compliance
The first and probably the most critical stage in addressing a DMARC fail error is ensuring that the domain’s SPF and DKIM records have been set up and configured for compliance with DMARC.

SPF is a protocol that stops spammers from relaying messages in your domain by checking the IP address of the sender with the IPs listed in the DNS record of that domain.

These guidelines should be followed:

• You should regularly check and update your SPF records to contain all the legitimate third-party IP addresses that otherwise send emails on your behalf.
• DKIM, on the other hand, provides an additional unique signature for your emails and is checked by the latter’s DK server using a key that you have set in your DNS records.
• The first thing to avoid is making sure your DKIM signatures are set up correctly and that the current mail is indeed signed with that particular proper private key, which belongs to that public key within your DNS section.
• SPF and DKIM are significant in passing the DMARC check, and failure in either SPF or DKIM will lead to DMARC failure. Hence, make sure to verify these settings. For example, check the SPF records to ensure they are correct, and the same applies to DKIM signatures; make sure they are set up correctly.

Change your DMARC Policy
Another proper method that can help overcome DMARC failure errors is modifying the management of DMARC policy. DMARC policy outlines the reception policy for messages that fail the DMARC check on the receiving mail server.

There are three policy options: There are three types, namely reject, quarantine, and none. If your current DMARC policy is rejected, all the emails that fail the DMARC check will not be delivered to the recipient’s inbox.

Though this is the most secure way, it sometimes rejects legitimate messages with SPF or DKIM problems.

Sometimes, it is possible to change the policy for some time to quarantine or not to find the issue with the email delivery without affecting the process.

Quarantine places the received emails in the recipient’s spam or junk folder to enable the recipient to go through them.

The least restrictive is None, whereby emails are sent within their usual fashion to the recipients, but messages informing you of failed deliveries are provided to you.

It is not the safest option and should only be used for a short while, but using it means you can get information on why DMARC failure is happening without affecting the delivery of the emails.

When it becomes easier to modify or arrange, you can ease back until you get to an even tighter X-Ray view.

Regularly Review and Update DMARC Records and Policies for Better Email Security
You need to ensure that you have taken the time to check your DMARC records often so that your email security is strong.

DMARC reports help reveal how the receiving servers’ emails are being processed by the domain, such as failure or error records, SPF, DKIM, or failure to align.

If you still want to analyze DMARC regularly, analyzing these reports to establish common themes that fail DMARC is possible.

For instance, if a given e-mail service or server constantly results in a failed SPF check, your current SPF record may require adding the particular server’s IP address.

Likewise, suppose the DKIM signatures are often insufficient. In that case, one should find out whether the process of signing is conducted correctly and whether the keys in the DNS records correspond to the keys applied to the emails.

Further, as your organization evolves or modifies, it might be necessary to include more IP addresses in the SPF record, regularly change the DKIM keys to enhance security, or update your DMARC method to fit the changing requirements of your domain.

Notably, such records and policies need to be updated and improved regularly to maintain the domain’s security and secure the delivery of legitimate emails.

Get Know a Way to Prevent a DMARC Failure from Happening and Also Learn the Methods of How to Check for DMARC Failures in Your Email Campaigns.