Summary
Setting a DMARC policy, especially to p=reject, is a critical step in enhancing email security and deliverability. While p=none is useful for initial monitoring, the ultimate goal for strong domain protection is to reach p=reject. This policy instructs receiving mail servers to outright reject emails that fail DMARC authentication, preventing fraudulent emails from reaching inboxes. However, implementing p=reject requires careful planning and a thorough understanding of all legitimate email streams originating from your domain. A phased approach is generally recommended to avoid inadvertently blocking valid emails.
Key findings
- DMARC Goal: The primary objective of DMARC implementation is to reach a p=reject policy, ensuring that unauthenticated emails are blocked from recipients.
- Policy Actions: A p=reject policy directs mailbox providers to refuse messages that fail DMARC authentication, whereas p=quarantine sends them to the spam folder, and p=none only monitors.
- Security Benefits: A robust DMARC policy, such as p=reject, significantly protects an organization against email spoofing and phishing attacks.
- Phased Approach: Best practices recommend a gradual progression from p=none to p=quarantine, and finally to p=reject, often utilizing the pct tag to enforce policies on a percentage of mail.
Key considerations
- Accurate Mail Streams: Before moving to p=reject, ensure all legitimate email sources are properly authenticated with SPF and DKIM.
- DMARC Reports: Regularly reviewing DMARC aggregate and forensic reports is crucial to identify any legitimate emails that are failing authentication, as discussed in our guide on understanding and troubleshooting DMARC reports.
- Impact on Forwarding: Email forwarding can sometimes cause DMARC failures, especially with a p=reject policy, as the forwarded message may break SPF alignment.
- BIMI Requirements: To leverage BIMI (Brand Indicators for Message Identification), a DMARC policy of at least p=quarantine or p=reject is often required, as detailed in this article on DMARC implementation.
- Subdomain Policy: Understand whether your DMARC policy applies to your root domain, subdomains, or both. Our guide on DMARC policies for organizational domains and subdomains can provide more context.
What email marketers say
Email marketers often approach setting DMARC p=reject with a mix of confidence and caution. While many recognize p=reject as the ideal state for security and brand protection (especially for BIMI compliance), they are keenly aware of the risks. The primary concern is inadvertently blocking legitimate email, particularly from unknown or unauthenticated mail streams. Marketers emphasize the importance of thorough preparation, continuous monitoring of DMARC reports, and understanding the full scope of a domain's email sending infrastructure before making the leap to p=reject.
Key opinions
- Confidence is Key: If a sender is highly confident in their email authentication (SPF and DKIM) for all outgoing mail, setting p=reject is seen as a viable and beneficial option.
- DMARC Policy Meanings: Marketers understand p=none for monitoring, p=quarantine for spam folder placement, and p=reject for outright blocking of unauthenticated mail.
- BIMI Necessity: For brands aiming to implement BIMI, a p=reject (or p=quarantine) policy is often a prerequisite, driving the push for stronger DMARC enforcement.
- Discovering Unknown Mail Streams: A significant challenge noted by marketers is identifying all legitimate email sending sources within an organization that may not yet be authenticated before moving to p=reject.
Key considerations
- Phased Transition: It is generally advisable to remain at p=none and thoroughly review DMARC reports for several months before progressing to stricter policies. See our guide on how to safely transition your DMARC policy.
- Impact on Redirects: Implementing p=reject can cause issues with email redirection, where messages from one mailbox are forwarded to another, potentially leading to DMARC authentication failures. This is especially relevant for discussion lists.
- Monitoring DMARC Reports: Even with high confidence in authentication, continuous monitoring of DMARC reports (via Google Postmaster Tools, for example) is crucial to catch any unexpected failures or spoofing attempts.
- Subdomain Scope: Verify if the DMARC policy is intended to apply to your primary domain, subdomains, or both, as this impacts its enforcement scope. This is important for ensuring a strong DMARC policy.
An Email Geeks marketer states that setting DMARC to p=reject is acceptable if you are highly confident in the authenticity of your outgoing mail. This policy acts as a strong enforcement mechanism against unauthorized email.
A marketer from Email Geeks explains that p=none is for gaining understanding of your mail streams, p=quarantine is for accepting mail but moving it to spam, and p=reject is for outright blocking unauthenticated emails.
What the experts say
Email deliverability experts universally agree on the strategic importance of adopting a p=reject DMARC policy for robust email security and brand protection. Their insights underscore the necessity of a methodical approach, emphasizing that the transition from monitoring to enforcement should be data-driven. Experts frequently highlight the hidden complexities of email infrastructure, such as unknown sending services and the nuances of mail forwarding, which can lead to legitimate emails being blocked if not meticulously accounted for. They strongly recommend using DMARC reports to uncover these potential pitfalls before fully enforcing a p=reject policy.
Key opinions
- Gradual Enforcement: Experts advise a slow and measured approach to DMARC policy enforcement, typically starting with p=none to gather data before moving to p=quarantine and then p=reject.
- Identify Mail Streams: A crucial step before p=reject is to use DMARC reports to identify all legitimate email sending services that use your domain and ensure they are properly authenticated.
- Mitigate Spoofing: Moving to p=reject significantly reduces the risk of third parties spoofing your domain for malicious purposes, protecting your brand reputation.
- Receiver Autonomy: Despite sender policies, the ultimate decision on how to handle DMARC failures rests with the receiving mail server, which may sometimes treat p=reject and p=quarantine similarly.
Key considerations
- Validation of All Sources: Ensure that all legitimate email sources, including third-party services (e.g., Google Workspace, recruiting apps, help desk software), are correctly configured with SPF and DKIM to align with your DMARC record before moving to enforcement.
- Review DMARC Reports: Actively review DMARC aggregate reports to identify any legitimate mail streams that are failing authentication, as these will be rejected once p=reject is in place. Our article on best practices for DMARC implementation provides more detail.
- Potential for Rejection: Be aware that some legitimate mail, particularly those affected by forwarding or complex routing, might still be rejected even with a correctly configured p=reject policy.
- Domain Scrutiny: Ensure the domains used in the From, Return-Path, and DKIM d= tags are correctly aligned, as misconfiguration can lead to blanket rejections.
- Cost/Benefit Analysis: While p=reject is the ideal, consider the effort required to reach this state versus the benefits, especially if there are many complex mail streams. More details can be found in this guide on DMARC best practices.
An expert from Email Geeks suggests monitoring DMARC reports, either manually or with a tool, to discover unexpected mail streams and potential third-party spoofing of your domain. This proactive approach helps prevent legitimate emails from being rejected.
An expert from Spam Resource advises that without proper DMARC authentication, various legitimate mail streams from your organization, such as those from Google Apps, recruiting, or help desk software, might be rejected when a p=reject policy is implemented.
What the documentation says
Official documentation and authoritative sources consistently advocate for a p=reject DMARC policy as the ultimate security posture. They outline the distinct actions associated with p=none, p=quarantine, and p=reject, emphasizing p=reject's role in completely blocking unauthenticated mail. The recommended best practice is to adopt a phased approach, leveraging the pct tag to gradually increase enforcement. This systematic transition minimizes disruption while maximizing protection against spoofing and phishing.
Key findings
- Policy Enforcement: A p=reject policy instructs email receivers to not accept messages that fail DMARC authentication, effectively blocking them.
- Protection against Spoofing: Enabling a DMARC policy, particularly p=reject, is crucial for protecting an organization against email spoofing and phishing, preventing malicious emails from reaching recipients.
- Phased Implementation: The recommended approach to DMARC implementation is a phased progression, starting with monitoring (p=none), then quarantining (p=quarantine), and finally rejecting (p=reject).
- PCT Tag Utilization: The pct tag is commonly used to advance policies, allowing senders to gradually increase the percentage of emails to which the DMARC policy applies, moving towards pct=100 with p=reject.
Key considerations
- DMARC Policy Significance: The DMARC p tag specifies how email service providers should handle incoming emails that fail DMARC authentication, offering reject, quarantine, or none as options.
- Avoid P=none Long-term: While useful for monitoring, a p=none policy should not be a permanent solution as it can pose security risks by not enforcing authentication. Our guide on simple DMARC examples explains initial setup.
- Troubleshooting Failures: If DMARC fails, common solutions include enabling or fixing SPF and DKIM authentication and adjusting your DMARC policy or authentication of your domain.
- Comprehensive Strategy: A full DMARC implementation strategy involves familiarizing yourself with policy implications, applying the pct tag, deliberately progressing policies, and ensuring ongoing DMARC maintenance. This forms part of the DMARC policy advancement.
Mailgun documentation states that p=reject is considered the ultimate goal of DMARC implementation. While p=quarantine is a good starting point, preventing spoofed emails from consistently landing in spam folders requires the stricter reject policy.
The 101domain Blog recommends adopting a phased approach to DMARC, particularly when implementing p=reject or p=quarantine. This signifies a strategic move towards stronger email authentication.
