Why are legitimate emails blocked when DMARC policy is higher than p=none?
Matthew Whittaker
Co-founder & CTO, Suped
Published 9 Jun 2025
Updated 17 Aug 2025
9 min read
Moving your DMARC policy beyond p=none (monitor-only mode) to an enforcement policy like p=quarantine or p=reject is a crucial step for domain security. It tells receiving mail servers how to handle emails that fail DMARC authentication, preventing malicious actors from spoofing your domain. The expectation is that this only affects fraudulent emails.
However, it's not uncommon for legitimate emails to unexpectedly get blocked or sent to spam when a stricter DMARC policy is implemented. This can be a perplexing and frustrating experience, especially when you believe all your legitimate sending sources are properly authenticated.
The primary reason for this paradox is almost always an issue with how the legitimate emails are being authenticated, or a misconfiguration that wasn't apparent under a p=none policy. DMARC simply enforces the authentication checks (SPF and DKIM alignment) that should already be in place. If these checks fail, a stricter policy will then instruct the receiving server to take action.
Understanding why these legitimate emails get flagged is key to troubleshooting and ensuring smooth email delivery. This guide will explore the common pitfalls that lead to legitimate emails being blocked, even with an enforced DMARC policy.
DMARC, or Domain-based Message Authentication, Reporting, and Conformance, is an email authentication protocol designed to give domain owners control over unauthorized use of their domain. It builds upon two existing authentication methods: SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail).
DMARC policies dictate how receiving mail servers should treat emails that claim to be from your domain but fail DMARC checks. The three main policy types are:
p=none: This is the monitoring policy. Emails that fail DMARC are still delivered, but you receive reports (RUA/RUF) about what's failing. It's a crucial first step for gathering data on your sending infrastructure, and understanding the implications of using a p=none policy.
p=quarantine: Emails that fail DMARC are sent to the recipient's spam or junk folder. This is a step towards enforcement, as it mitigates the risk of spoofing without outright blocking. Learn more about what a DMARC policy is.
p=reject: Emails that fail DMARC are completely rejected and not delivered to the inbox or spam folder. This provides the highest level of protection against spoofing. You can find out how to use DMARC p=reject to combat spoofing.
For DMARC to pass, an email must also pass either SPF or DKIM authentication, and the domain in the From: header must align with the domain that passed SPF or DKIM. If this alignment fails, even for legitimate mail, DMARC will fail. This is why legitimate emails sometimes fail DMARC.
Policy
Action on Failure
Purpose
p=none
No action, email delivered as usual.
Monitoring and reporting only. Allows data collection without impacting delivery.
p=quarantine
Email is typically moved to spam/junk folder.
Enforces a mild policy, reducing spoofing without hard blocks.
The primary reason legitimate emails get blocked by DMARC enforcement is a failure in SPF or DKIM authentication, or a lack of proper alignment. This often stems from:
Misconfigured SPF or DKIM for legitimate services
Many organizations use third-party email service providers (ESPs), customer relationship management (CRM) systems, or other marketing automation platforms to send emails on their behalf. If the SPF records for your domain don't include these sending sources, or if their DKIM signatures aren't correctly configured to align with your domain, DMARC will fail. For instance, if your emails are failing DMARC checks despite seemingly correct SPF and DKIM, this is a prime suspect. For more on this, read why DMARC is failing.
Don't rush enforcement
Implementing a DMARC policy of p=reject (or even p=quarantine) too quickly, especially from p=none, without thorough monitoring of DMARC reports is a common pitfall. This can cause significant deliverability issues for legitimate mail. It's imperative to use p=none for a period of time to identify all legitimate sending sources.
Email forwarding is a common culprit. When an email is forwarded, particularly through older or less sophisticated forwarding services, the email's headers or content might be modified. This modification can break the original DKIM signature, leading to a DMARC authentication failure upon receipt. This is an edge case that can cause legitimate emails, like calendar invites forwarded through services such as Google Calendar, to be rejected by recipients, particularly those on Microsoft platforms, if their DMARC policy is p=reject or p=quarantine.
Unauthorized or 'rogue' sending
Sometimes, different departments or individuals within an organization might use unauthorized email sending tools (e.g., a new marketing tool or a departmental CRM) that haven't been properly configured with SPF or DKIM for your domain. These are legitimate emails from your organization's perspective, but they will fail DMARC checks because they lack the necessary authentication, potentially leading to your emails going to spam.
Beyond DMARC: Reputation and overrides
Even if your DMARC records are impeccable and your emails pass all authentication checks, deliverability is not solely dependent on DMARC. Mailbox providers (MBPs) assess various factors to determine inbox placement, including sender reputation, content quality, and recipient engagement.
A sender with a poor historical reputation for sending unwanted mail or hitting spam traps, even if technically authenticated via DMARC, may still find their emails blocked or routed to the spam folder. DMARC merely provides the identity; the reputation attached to that identity is what truly dictates where the email lands. It makes it easier for the MBP to confirm your verified identity so it can confidently block or filter based on your domain's sending history.
Another less common but possible scenario is that a mailbox provider might have a local override policy that supersedes your published DMARC record. While uncommon, some providers may have internal rules or specific blocklists (or blacklists) that can affect even perfectly authenticated emails, especially if there are other concerning factors related to the sending IP or domain.
DMARC failure (authentication issue)
Cause: SPF or DKIM records are missing, incorrect, or misaligned with the From: header domain.
Impact: Emails are quarantined or rejected based on your DMARC policy setting (e.g., p=quarantine, p=reject). This issue is directly fixable by adjusting your DNS records or ESP settings.
Troubleshooting: Analyze DMARC aggregate reports to identify sources failing authentication and correct the underlying SPF/DKIM issues. You can understand and troubleshoot DMARC reports.
Reputation-based blocking (content/sender issue)
Cause: Even if DMARC passes, a low sender reputation due to high spam complaints, sending to inactive addresses (spam traps), or poor engagement can lead to blocking. Mailbox providers might also use internal blocklists.
Impact: Emails land in spam or are rejected by the recipient's server, regardless of DMARC authentication status. This goes beyond DMARC policy, as the email is identified as legitimate but undesirable. Find out what to do when emails are blocked.
Troubleshooting: Focus on list hygiene, content quality, and recipient engagement. Monitor your domain reputation via tools like Google Postmaster Tools.
Safely transitioning your DMARC policy
The safest and most recommended approach for DMARC implementation is a gradual one. Start with a p=none policy and use the DMARC reports to identify all legitimate sending sources. This allows you to see which emails are failing authentication without affecting delivery.
Once you're confident that all your legitimate email streams are correctly authenticated and aligned, you can then incrementally move to p=quarantine, and eventually p=reject. This phased approach, documented in guides like DMARC Explained: Five Steps to Email Authentication, allows you to catch and fix issues before they impact your deliverability. Additionally, you can find a simple DMARC example with p=none policy.
DMARC aggregate (RUA) reports are your most valuable tool during this process. They provide detailed XML data showing which sources are sending email on behalf of your domain and whether they are passing or failing DMARC. These reports are crucial for identifying legitimate senders that need SPF or DKIM adjustments. Also, be aware that while the pct (percentage) tag exists to apply policies to a subset of emails, its implementation is not always consistent across all mailbox providers and may be deprecated in future DMARC revisions.
Regularly reviewing these reports and making necessary adjustments to your DNS records (SPF, DKIM, DMARC) or third-party sending configurations is paramount. This proactive approach will help you maintain strong authentication for all your legitimate email streams, ensuring they reach the inbox even with a strict DMARC policy in place. For more guidance, read how to safely transition your DMARC policy.
Views from the trenches
Best practices
Start with DMARC p=none and analyze aggregate reports to identify all legitimate sending sources.
Ensure all third-party email service providers are correctly configured with SPF and DKIM authentication.
Regularly review DMARC reports and update DNS records as new sending sources are added.
Educate internal teams about authorized email sending channels and discourage 'rogue' sending.
Prioritize list hygiene and maintain good sender reputation, as it complements DMARC.
Implement a phased approach for DMARC enforcement, moving from none to quarantine, then to reject.
Common pitfalls
Jumping directly to p=quarantine or p=reject without first analyzing DMARC reports.
Forgetting to add new legitimate sending services (ESPs, CRMs) to your SPF record or set up DKIM.
Ignoring DMARC aggregate reports, missing crucial data on authentication failures.
Assuming DMARC guarantees deliverability, overlooking sender reputation and content quality.
Not accounting for email forwarding that can break DKIM signatures, leading to legitimate mail failure.
Having multiple DMARC records, which can interfere with domain authentication.
Expert tips
The volume of legitimate emails failing due to weird issues like forwarding is usually low, but it's an ongoing challenge.
Authentication establishes a base for mailbox providers to anchor your domain's sending reputation.
If DMARC passes but emails are still blocked, the issue is likely reputation-related, not DMARC itself.
While pct=100 is the default and doesn't need to be explicitly included, the pct tag itself is inconsistent.
Network or DNS problems can cause email failures generally, not just with DMARC. This is a common issue for email sending.
Always use DMARC reports to ensure you catch any legitimate emails failing authentication.
Expert view
Expert from Email Geeks says DMARC failures often stem from misconfigured SPF or DKIM in email platforms, or issues like email forwarding rewriting headers and breaking signatures.
2024-09-12 - Email Geeks
Expert view
Expert from Email Geeks says authentication allows mailbox providers to establish a sender's reputation tied to the authenticated identity, even if other best practices are not followed.
2024-09-12 - Email Geeks
Your path to DMARC enforcement
Moving to a DMARC policy higher than p=none is a critical step in securing your domain from email spoofing and phishing attacks. While it's designed to block malicious emails, legitimate emails can sometimes fall victim due to various issues, primarily related to misconfiguration or failure in SPF and DKIM alignment.
The key to successful DMARC enforcement without impacting legitimate mail lies in a systematic, phased implementation. By starting with a p=none policy and meticulously analyzing your DMARC aggregate reports, you can identify all your sending sources and ensure they are properly authenticated. This allows you to correct any issues proactively before switching to a stricter policy.
Ultimately, DMARC is a powerful tool for improving your email security and deliverability. By addressing authentication gaps, ensuring proper alignment, and maintaining a strong sender reputation, you can successfully implement enforcement policies and safeguard your domain, ensuring your legitimate emails reach their intended recipients. If your emails are going to spam, DMARC is often a key part of the solution.
Google Calendar, to be rejected by recipients, particularly those on 
Microsoft platforms, if their DMARC policy is p=reject or p=quarantine.
