Why might an email provider not honor a DMARC p=reject policy?
Matthew Whittaker
Co-founder & CTO, Suped
Published 23 Jun 2025
Updated 19 Aug 2025
8 min read
DMARC p=reject policy is the strongest enforcement option available to domain owners. It instructs receiving mail servers to outright reject emails that fail DMARC authentication. The intention is clear: prevent fraudulent emails (spoofing) from reaching inboxes. However, despite this explicit instruction, you might encounter situations where an email provider (mailbox provider, or MBP) doesn't fully honor a p=reject policy. This can be perplexing, especially when you're trying to secure your domain and ensure legitimate mail delivery.
The expectation is that any email failing DMARC with a p=reject policy should be bounced back to the sender, never making it into the recipient's inbox or even their spam folder. When this doesn't happen, it raises questions about the effectiveness of your DMARC implementation and why your security measures aren't being fully respected.
I've seen many instances where this scenario plays out, leading to confusion and frustration for senders who have diligently set up their DMARC records. It highlights a critical aspect of email deliverability: while you control your domain's authentication policies, the final decision on how to handle incoming mail rests with the receiving server. Understanding the various reasons behind these policy overrides is key to troubleshooting and improving your email program.
It's crucial to understand that a DMARC policy, even a p=reject, is essentially a suggestion from the sending domain to the receiving mail server. While most reputable providers strive to honor DMARC policies for better email security, they ultimately reserve the right to make their own decisions based on a multitude of factors. This autonomy allows them to protect their users from potential false positives or to prioritize other internal security measures.
Some mailbox providers (MBPs) might have a more lenient approach, especially if they are concerned about rejecting legitimate emails due to complex mail flows or misconfigurations on the sender's side. For instance, some providers might treat a p=reject as a p=quarantine, moving the failed emails to spam or junk folders instead of outright rejecting them. This gives recipients a chance to retrieve the email if it was a false positive, albeit at the cost of the sender's desired enforcement.
It's also worth noting that DMARC is part of a larger ecosystem of email authentication and reputation signals. A receiving server may consider other factors like sender reputation, content analysis, and user complaints when deciding the final disposition of an email, even if it fails DMARC validation with a reject policy. A low sender reputation, for example, could lead to legitimate emails being treated harshly, even with proper DMARC setup.
DMARC policy is a suggestion
Despite its strong directive, the p=reject policy is not a mandatory command. Receiving mail servers retain ultimate control over how they process incoming mail.
Common reasons for DMARC policy overrides
There are several specific scenarios and configurations that can lead to an email provider not honoring a DMARC p=reject policy. One common reason is policy overrides. Mailbox providers may have their own internal security policies that take precedence over external DMARC policies. For example, a trusted sender list could allow emails from specific domains to bypass DMARC checks, or a global whitelist might override individual domain policies. This is a deliberate choice by the receiving server to manage its inbound mail flow.
Another factor is email forwarding. When an email is forwarded, it often breaks DKIM signatures or SPF alignment, causing DMARC to fail for what was originally a legitimate email. To prevent legitimate forwarded mail from being rejected, some providers may choose to deliver these messages to the spam folder rather than discarding them entirely, even if the domain has a p=reject policy. This is a compromise to ensure deliverability for valid, albeit re-routed, communications.
Furthermore, the pct tag in your DMARC record can also play a role. If you've set pct to less than 100, you are explicitly telling receiving servers to apply the policy to only a percentage of failing messages. While some providers might not strictly honor the pct tag and apply the policy fully, others may disregard it entirely, or interpret it in a way that allows a portion of non-compliant mail to be delivered. This is less about deliberate circumvention of p=reject and more about how different providers parse and implement optional DMARC directives. You can read more about DMARC policy overrides if you need additional context.
Reason for Override
Impact on Deliverability
Potential Mitigation
Internal policies and trusted sender lists (whitelisting)
Legitimate DMARC-failing emails from trusted sources are delivered to the inbox or spam, bypassing rejection.
Review DMARC reports to identify false negatives. Contact the receiving MBP's postmaster.
Email forwarding
Forwarded emails, even legitimate ones, fail DMARC and may be sent to spam instead of being rejected. This is especially true if DKIM breaks.
Ensure SPF and DKIM are correctly configured for all sending sources. Monitor DMARC reports for forwarded mail.
DMARC pct tag not fully honored
More than the specified percentage of failing emails might be rejected or quarantined, or the tag is ignored entirely.
Verify pct tag behavior through DMARC reports. Consider if pct is appropriate for your desired policy.
Impact on legitimate email and deliverability
When an email provider doesn't honor your p=reject policy, the primary impact is on your domain's security and your email deliverability. While the goal of p=reject is to stop unauthorized emails dead in their tracks, if a provider merely quarantines them or, worse, delivers them to the inbox, your efforts to combat spoofing are undermined. This can lead to increased phishing attacks impersonating your brand, eroding trust with your recipients.
The lack of strict enforcement can also skew your perception of your DMARC compliance. If you expect messages to be rejected but they're only quarantined, you might not fully realize the extent of unauthorized email activity or the underlying authentication issues. This is why DMARC monitoring is so critical, as it provides the necessary visibility into how different receiving servers are actually handling your mail.
Furthermore, consistent non-compliance by receiving servers, even if they aren't fully honoring the reject policy, could impact your domain's overall reputation. If a provider repeatedly sees emails that fail DMARC authentication from your domain, regardless of your stated policy, it might negatively affect how they view your sending practices. This could eventually lead to your legitimate emails experiencing lower inbox placement or even being added to internal blocklists (or blacklists).
Security impact
If p=reject isn't fully honored, malicious emails impersonating your domain might still reach user inboxes or spam folders, increasing the risk of phishing attacks.
Deliverability impact
Legitimate mail could be inadvertently affected if the provider's override rules are too broad. Also, ongoing DMARC failures, even if not fully rejected, can negatively impact your sender reputation, leading to lower inbox rates for valid emails.
Troubleshooting and best practices
To address situations where your p=reject policy isn't fully honored, the first step is always thorough investigation. Start by analyzing your DMARC aggregate reports. These reports provide invaluable insights into how different MBPs are processing your mail, including their DMARC dispositions (reject, quarantine, none). Look for discrepancies where emails that should have been rejected are instead quarantined or delivered.
If you identify a specific provider consistently failing to honor your p=reject policy, a good next step is to reach out to their postmaster team. Many providers, like Yahoo, are transparent about their DMARC enforcement policies and might be able to offer specific guidance or confirm their behavior. Be prepared to provide specific examples and DMARC report snippets.
Finally, ensure your own DMARC implementation is robust. Double-check your SPF and DKIM records for proper configuration and alignment. If you're transitioning to p=reject, follow best practices for safe deployment, gradually moving from p=none to p=quarantine, and then to p=reject while closely monitoring reports. This phased approach helps catch issues before they lead to widespread deliverability problems.
Actively monitor DMARC aggregate reports to detect how mail is being handled by various MBPs.
Maintain consistent and correct SPF and DKIM configurations across all legitimate sending sources.
Establish relationships with MBP postmaster teams for specific policy interpretation queries.
Gradually implement DMARC policies, starting with p=none, then quarantine, before moving to reject.
Common pitfalls
Assuming all MBPs strictly adhere to a p=reject policy without verifying via reports.
Overlooking email forwarding chains that break SPF or DKIM, leading to legitimate mail failures.
Not accounting for internal MBP policies or trusted sender lists that may override DMARC directives.
Setting a p=reject policy without sufficient data or proper authentication of all sending sources.
Expert tips
Always remember DMARC policies are suggestions, not mandates, to receiving mail servers.
Regularly review your DMARC reports for anomalies in policy enforcement from different providers.
If an MBP doesn't honor p=reject, consider it a potential indicator of a broader reputation issue for your domain.
Be aware that some providers, like Microsoft, have historically treated p=reject as p=quarantine.
Expert view
Expert from Email Geeks says a DMARC p=reject policy is a suggestion from the sender and not a strict requirement for the receiver. This means mail providers can choose to process emails differently.
2023-06-22 - Email Geeks
Marketer view
Marketer from Email Geeks says Microsoft historically treated p=reject as quarantine, not a true rejection, which illustrates that not all MBPs honor the exact policy.
2023-06-23 - Email Geeks
Navigating DMARC policy variations
While a DMARC p=reject policy is your strongest defense against email spoofing, it's not a universal guarantee that all email providers will honor it in every scenario. Factors such as internal policies, email forwarding, and even the implementation of the pct tag can lead to deviations from your desired policy enforcement. This underscores the importance of continuous monitoring and a nuanced understanding of how different MBPs handle DMARC.
By proactively monitoring your DMARC reports, understanding potential policy overrides, and maintaining strong authentication practices, you can better navigate these complexities. This approach ensures that your legitimate emails reach the inbox while maximizing your domain's protection against unauthorized use, even when providers don't strictly adhere to a p=reject policy.
