Summary
Effective DMARC setup involves a cautious, phased deployment, starting with a 'p=none' policy to gather data from aggregate (RUA) reports without impacting email delivery. This initial monitoring phase is vital for identifying all legitimate sending sources and ensuring their proper authentication with SPF and DKIM. Once all authorized senders are correctly configured and aligned, organizations can gradually escalate the policy to 'p=quarantine' and ultimately to 'p=reject' for maximum protection against spoofing and phishing. Continuous analysis of DMARC reports is essential throughout this process for refining policies and addressing any authentication issues. Subdomain policies should also be considered; while they often inherit the organizational policy, explicit 'sp' tags can be used for specific security needs, such as rejecting mail from unused subdomains, enhancing overall email security.
Key findings
- Phased Rollout: The most effective DMARC implementation follows a phased approach: begin with 'p=none' for monitoring, then progress to 'p=quarantine' to isolate suspicious emails, and finally to 'p=reject' for the strongest protection against impersonation.
- RUA Reports are Essential: Aggregate (RUA) reports are crucial for monitoring DMARC compliance, offering comprehensive overviews of authentication results without exposing sensitive data, making them safer and sufficient for most monitoring needs.
- Prerequisites for Strictness: Before moving to stricter DMARC policies like 'quarantine' or 'reject', all legitimate email sending sources must be identified and properly authenticated with SPF and DKIM records to prevent legitimate emails from being blocked.
- Subdomain Policy ('sp' tag): Subdomains inherit the main domain's DMARC policy by default if the 'sp' tag is omitted. However, explicit 'sp' tags can be set to enforce specific security measures, such as 'sp=reject' for non-sending or parked subdomains.
- Alignment is Crucial: For DMARC to pass, either SPF or DKIM must pass authentication, and their respective domains must be aligned with the 'From:' header domain, which is fundamental for proper DMARC enforcement.
Key considerations
- Monitoring and Data Analysis: Diligently analyze aggregate DMARC reports (RUA) to identify authentication failures, legitimate senders, and potential spoofing attempts. Utilizing a DMARC reporting service is essential to parse and visualize this data effectively.
- Cautious RUF Use: While forensic (RUF) reports offer detailed failure data, use them cautiously due to potential privacy concerns and their voluminous nature; they are generally recommended only for specific forensic investigations or with trusted entities.
- Organizational Reporting: Ensure the organizational domain is configured to receive DMARC reports, providing essential visibility into email streams across all levels.
- Subdomain Strategy: Determine whether subdomains should inherit the main policy or have specific policies. Setting 'sp=reject' for unused or parked subdomains can enhance security, while active subdomains should align with the main domain's phased rollout.
- Continuous Refinement: DMARC deployment is an ongoing process requiring continuous monitoring and adjustment based on report analysis to ensure optimal protection and legitimate mail flow.
What email marketers say
9 marketer opinions
Implementing DMARC effectively requires a methodical, step-by-step approach, starting with a 'p=none' policy to safely observe email traffic and gather essential data. This initial phase, leveraging aggregate DMARC reports, is crucial for identifying all legitimate email sending services and ensuring their proper authentication with SPF and DKIM. Only after achieving comprehensive visibility and resolving any authentication failures for authorized senders should an organization gradually escalate its DMARC policy to 'p=quarantine' and ultimately to 'p=reject', which provides the strongest protection against impersonation and spoofing. Subdomains also play a significant role; while they often inherit the primary domain's policy, employing specific 'sp' tags, such as 'sp=reject' for inactive or parked subdomains, can further enhance overall email security. Ongoing analysis of DMARC reports is vital for refining policies and maintaining deliverability.
Key opinions
- Gradual Policy Enforcement: The most robust DMARC implementation follows a careful, incremental progression from a monitoring policy ('p=none') to an enforcement policy ('p=quarantine' or 'p=reject') to prevent service disruption.
- Aggregate Reports are Key: Aggregate (RUA) DMARC reports are indispensable for gaining insight into email authentication results, providing the necessary data to identify legitimate senders, detect spoofing attempts, and guide policy adjustments.
- Pre-Requisite Authentication: Before moving to stricter DMARC enforcement, it is imperative to identify all legitimate email sending sources and ensure they are correctly configured with DMARC-aligned SPF and DKIM records to prevent unintended email blocking.
- Subdomain Policy Flexibility: The 'sp' (subdomain policy) tag allows for distinct DMARC policies for subdomains, enabling organizations to apply stricter rules like 'sp=reject' for unused subdomains while maintaining a phased approach for active ones.
- Alignment is Fundamental: A DMARC pass hinges on at least one of SPF or DKIM passing authentication and having its domain properly aligned with the 'From:' header domain, underscoring the importance of correct configuration.
Key considerations
- Thorough Sender Discovery: A critical first step in DMARC deployment is exhaustively identifying every service and application that sends email on behalf of your domain to ensure they are all properly authenticated.
- Continuous Report Analysis: Regularly analyze DMARC aggregate reports using a dedicated service to understand authentication trends, troubleshoot issues with legitimate email, and quickly detect any unauthorized sending activities.
- Strategic Subdomain Management: Develop a clear strategy for subdomain policies; consider setting 'sp=reject' for subdomains not intended to send email, while aligning active subdomains' policies with the main domain's rollout.
- Prioritize RUA Over RUF: While forensic (RUF) reports offer detailed failure data, aggregate (RUA) reports are generally preferred for ongoing monitoring due to privacy concerns and the comprehensive, summarized data they provide without exposing sensitive content.
- Avoid Hasty Enforcement: Rushing to a 'quarantine' or 'reject' policy without adequate preparation can lead to legitimate emails being blocked, emphasizing the need for patience and data-driven policy changes.
Marketer view
Email marketer from Valimail Blog explains that a key DMARC best practice is to aim for a 'p=reject' policy to achieve the highest level of email authentication and protection against spoofing. Before reaching 'reject', organizations must ensure all legitimate email sources are properly identified and configured with SPF and DKIM records, emphasizing the critical role of DMARC reporting tools to gain visibility into all sending domains and subdomains.
25 Apr 2023 - Valimail Blog
Marketer view
Email marketer from Mailgun Blog shares that DMARC best practices include understanding and utilizing the sp (subdomain policy) tag. If the sp tag is omitted, subdomains inherit the organizational p policy. However, for specific use cases like parked domains or different sending patterns, explicitly setting sp=reject or sp=quarantine for subdomains, independent of the organizational policy, can enhance security. They also mention the pct tag for a gradual rollout percentage.
20 Aug 2023 - Mailgun Blog
What the experts say
3 expert opinions
A successful DMARC implementation hinges on a strategic, multi-stage approach, prioritizing comprehensive reporting and careful policy adjustments across both organizational and subdomain levels. Initially, a 'p=none' policy should be adopted to monitor email traffic and gather vital data, enabling organizations to identify legitimate sending sources and ensure their proper authentication with SPF and DKIM. As confidence grows, policies can be incrementally tightened to 'quarantine' and ultimately 'reject' for enhanced protection. Consistent DMARC reporting, especially at the organizational level, is critical for gaining insight into email streams, differentiating between authorized and unauthorized senders, and informing necessary policy refinements. Moreover, while subdomains often inherit the main domain's DMARC policy, the use of explicit 'sp' tags allows for tailored subdomain policies, contributing to robust overall email security.
Key opinions
- Phased Deployment: DMARC deployment should always begin with a 'p=none' policy to gather crucial data from reports, allowing for safe identification of legitimate sending sources before moving to stricter enforcement policies like 'quarantine' or 'reject'.
- Comprehensive Reporting: Actively receiving and analyzing DMARC reports, particularly at the organizational domain level, is paramount for gaining insight into email streams, distinguishing legitimate email from unauthorized usage, and guiding policy refinements.
- Prioritize Authentication: Before progressing to stricter DMARC policies, it is essential to ensure all authorized email sending sources are accurately identified and properly authenticated with DMARC-aligned SPF and DKIM records.
- Subdomain Policy Management: While subdomains typically inherit the main organizational DMARC policy, the 'sp' tag offers flexibility to define explicit, independent policies for specific subdomains, such as applying 'reject' for non-sending or parked ones.
- DMARC Alignment: Successful DMARC authentication relies on either SPF or DKIM passing and their respective domains aligning with the 'From:' header domain, which is a fundamental requirement for effective DMARC enforcement.
Key considerations
- Ensure Organizational Reporting: Configure the primary organizational domain to receive DMARC reports, ensuring a holistic view of email traffic and compliance across all associated subdomains.
- Strategic Subdomain Policies: Carefully determine whether subdomains should inherit the main policy or have their own explicit policies using the 'sp' tag, enabling tailored security measures for different subdomain usage.
- Proactive Report Analysis: Regularly analyze DMARC aggregate reports to understand authentication trends, identify legitimate senders, and promptly detect any instances of email spoofing or unauthorized sending.
- Validate All Legitimate Senders: Before increasing DMARC policy enforcement, conduct a thorough audit to identify and correctly configure all legitimate email sending services and applications with SPF and DKIM.
- Gradual Policy Escalation: Implement DMARC policies through a methodical, phased approach, starting with monitoring and only gradually advancing to 'quarantine' or 'reject' once complete visibility and proper authentication are confirmed.
Expert view
Expert from Email Geeks explains that the organizational domain should ideally receive DMARC reporting, indicating a current setup might not be receiving any. They also suggest that a subdomain DMARC policy may not need an explicit 'sp=' tag, and emphasize the importance of reporting at all levels, especially the organizational level, even when different DMARC policies are in place for various domain levels.
15 Dec 2024 - Email Geeks
Expert view
Expert from Spam Resource explains that DMARC implementation should follow a phased approach, starting with a 'p=none' policy for monitoring, then progressing to 'quarantine' and 'reject'. The article stresses the critical role of DMARC reports (RUA and RUF) for gaining insight into email streams and distinguishing between legitimate senders and unauthorized usage. It also notes that subdomains generally inherit the main organizational DMARC policy unless a specific subdomain policy is defined.
5 Aug 2021 - Spam Resource
What the documentation says
5 technical articles
Robust DMARC implementation is achieved through a deliberate, iterative process focused on gaining visibility into email flows and systematically strengthening policy enforcement. This journey begins with an initial 'p=none' policy, which allows organizations to thoroughly monitor email streams and collect aggregate DMARC reports without impacting mail delivery. This crucial phase helps identify all legitimate sending services and verify their proper authentication via SPF and DKIM. Once all authorized senders are validated and aligned, organizations can progressively transition to 'p=quarantine' and ultimately 'p=reject', significantly enhancing protection against spoofing and phishing. Effective DMARC management also requires careful consideration of subdomain policies, often utilizing explicit 'sp' tags to apply specific security measures, such as rejecting mail from unused subdomains, thereby fortifying the overall email security posture. Continuous analysis of DMARC reports is paramount for ongoing policy refinement.
Key findings
- Phased Policy Progression: The most effective DMARC setup progresses through distinct policy stages: 'p=none' for initial data collection and monitoring, followed by 'p=quarantine' to isolate unauthenticated mail, and finally 'p=reject' for outright blocking.
- Reporting Pillars: Aggregate (RUA) reports are fundamental for monitoring DMARC compliance and understanding email authentication trends, while forensic (RUF) reports, though offering granular detail, require cautious use due to privacy and volume concerns.
- Authentication Foundation: Successful DMARC enforcement relies on all legitimate email senders being properly identified and authenticated with DMARC-aligned SPF and DKIM records prior to stricter policy implementation.
- Flexible Subdomain Control: While subdomains typically inherit the main domain's DMARC policy, the 'sp' tag provides flexibility to set specific, independent policies for subdomains, which is valuable for tailored security, especially for non-sending ones.
- Alignment as a Core Principle: DMARC authentication success fundamentally depends on the alignment of either the SPF or DKIM domain with the email's 'From:' header domain.
Key considerations
- Iterative Deployment Approach: Adopt a methodical, multi-stage DMARC deployment, starting with a monitoring policy and gradually escalating enforcement only after comprehensive data analysis and sender validation.
- Strategic Use of Reporting: Regularly analyze aggregate DMARC reports to gain crucial insights into email streams, detect unauthorized activity, and inform policy adjustments, reserving forensic reports for specific, trusted investigations.
- Comprehensive Sender Identification: Before enforcing stricter DMARC policies, rigorously identify and configure all legitimate email-sending sources to prevent unintended blocking of valid mail.
- Tailored Subdomain Strategy: Develop a clear strategy for managing subdomain DMARC policies, considering the use of explicit 'sp' tags to apply stricter rules- e.g., 'reject'- for subdomains not intended for sending email.
- Continuous Policy Refinement: DMARC is not a set-it-and-forget-it solution; ongoing monitoring of reports and iterative adjustments to policies are essential to maintain optimal email deliverability and security.
Technical article
Documentation from DMARC.org explains that the best practice for DMARC setup involves a phased deployment, starting with a 'none' policy to monitor email streams and understand authentication failures, then moving to 'quarantine' to isolate suspicious emails, and finally to 'reject' to completely block unauthenticated mail. They also highlight the importance of rua reports for aggregate data and ruf reports for forensic analysis to understand DMARC enforcement.
16 Jun 2024 - DMARC.org
Technical article
Documentation from Google Workspace Admin Help explains that for DMARC setup, organizations should begin with a 'p=none' policy to monitor and collect DMARC reports without affecting mail delivery. This allows administrators to analyze authentication results for SPF and DKIM and identify legitimate sending sources before moving to stricter policies. They also emphasize the need for a DMARC reporting tool to analyze the aggregate reports (rua).
15 Oct 2022 - Google Workspace Admin Help
DMARC Policies for Organizational Domains and Subdomains Explained
How do I properly set up DMARC records and reporting for email authentication?
How to set up DMARC reports and what are the best practices?
What are the best practices for DMARC implementation, including tag definition and tool recommendations?
What are the best practices for setting up SPF, DKIM and DMARC for email authentication?
What is the best DMARC, DKIM, and SPF setup for marketing and transactional emails sent from different subdomains?
