Summary
Implementing DMARC, particularly the 'p=reject' policy, requires a strategic and cautious approach. Documentation explains 'p=reject' instructs recipient servers to reject messages failing authentication, offering the strongest protection against spoofing. However, experts and marketers emphasize careful planning is paramount. The consistent recommendation is to begin with 'p=none' to monitor traffic, identify authentication issues, and ensure proper SPF and DKIM configuration across all sending sources (ESP, CRM, etc.) before moving to stricter policies. DMARC reporting (via rua/ruf tags) is vital for understanding the impact of your policy and identifying potential problems. It is also important to understand DMARC alignment. DMARC enhances deliverability by preventing spoofing and phishing, but maintaining good sending practices remains essential.
Key findings
- Phased Implementation: A phased approach, starting with 'p=none' for monitoring, is recommended for DMARC implementation.
- Authentication Foundation: Correct SPF and DKIM configuration is crucial across all sending sources before enforcing 'p=reject'.
- Reporting Importance: DMARC reporting provides essential insights into policy impact and authentication failures.
- DMARC Alignment: Proper SPF and DKIM passing (alignment) are important for messages to pass DMARC authentication checks.
- Deliverability Boost: DMARC, particularly 'p=reject', improves deliverability by preventing spoofing and enhancing sender reputation.
- Reject Valid: 'p=reject' is stronger than 'p=none'.
Key considerations
- Premature Enforcement Risks: Implementing 'p=reject' prematurely can block legitimate emails if authentication is not properly configured.
- Comprehensive Source Audit: Audit and authenticate all email sending sources (ESP, CRM, etc.).
- Continuous Monitoring is needed: Regularly monitor DMARC reports to identify and address authentication issues and potential misconfigurations.
- Holistic Approach Required: DMARC is not a single solution; good sending practices are still needed to avoid blocklists.
- Expert Assistance: Reject without reporting can be problematic, monitoring and configuration is needed.
- Case Study Caution: Implementing p=reject requires support/guidance.
What email marketers say
11 marketer opinions
The advice regarding DMARC settings, particularly the 'p=reject' policy, emphasizes a cautious, phased approach. Starting with 'p=none' is widely recommended to monitor email traffic and identify authentication issues without disrupting delivery. Ensuring proper SPF and DKIM configuration is crucial before implementing stricter policies like 'p=reject' to prevent legitimate emails from being blocked. DMARC reporting plays a vital role in understanding the impact of your policy and identifying potential problems. DMARC alignment is also important, with proper SPF and DKIM passing being required for messages to pass DMARC authentication. While DMARC improves deliverability by preventing spoofing, it doesn't guarantee it and good sending practices are still important.
Key opinions
- Phased Approach: Implementing DMARC effectively requires a phased approach, starting with 'p=none' for monitoring and gradually increasing enforcement.
- Authentication First: Ensure SPF and DKIM are correctly configured for all email sending sources before implementing 'p=reject'.
- Reporting is Key: DMARC reporting is crucial for understanding the impact of your DMARC policy and identifying authentication failures.
- DMARC alignment: SPF and DKIM need to pass alignment checks for messages to pass DMARC authentication.
- Improved delivery: DMARC improves delivery, specifically by preventing spoofing and phishing attacks.
Key considerations
- Premature Rejection: Implementing 'p=reject' prematurely can block legitimate emails if SPF or DKIM are misconfigured.
- Complete Configuration: Ensure all email sending sources (ESP, CRM, etc.) are properly authenticated.
- Ongoing Monitoring: Continuously monitor DMARC reports to identify and address authentication issues.
- DMARC is not a panacea: While DMARC improves deliverability, it doesn't stop you from being blocklisted if you don't maintain good sending practices.
Marketer view
Email marketer from Valimail shares that starting with 'p=none' is a recommended practice. This allows you to monitor DMARC reports and identify any legitimate email sources that are failing authentication before moving to a stricter policy like 'p=quarantine' or 'p=reject'.
27 Jul 2021 - Valimail
Marketer view
Email marketer from Spamhaus explains that while DMARC helps protect against direct spoofing, it doesn't automatically prevent you from being blocklisted for other spam-related issues. You still need to maintain good sending practices.
12 Sep 2023 - Spamhaus
What the experts say
5 expert opinions
The expert opinions on DMARC settings, especially regarding 'p=reject', highlight the importance of careful planning and monitoring. While 'p=reject' offers strong protection against spoofing, it demands thorough understanding of email streams and proper configuration of SPF and DKIM. Starting with 'p=none' for monitoring is generally recommended, along with appropriate reporting mechanisms. There's a consensus that using 'p=reject' without adequate preparation and ongoing monitoring can lead to significant deliverability issues and blocking legitimate emails.
Key opinions
- Reject Valid: 'p=reject' is a valid and strong DMARC setting, stronger than 'p=none'.
- Monitoring is Crucial: Using DMARC 'reject' requires thorough monitoring to prevent issues.
- Preparation Needed: Proper SPF/DKIM setup is essential before enforcing 'p=reject'.
- Understand Email Streams: Understanding email streams is important for implementing DMARC.
Key considerations
- Advanced Practice: Using DMARC reject without reporting is an advanced practice and should be approached cautiously.
- Potential for Issues: Improper implementation of 'p=reject' can lead to deliverability problems and blocking legitimate emails.
- Ongoing Attention: Implementing 'p=reject' requires ongoing monitoring and adjustments to ensure legitimate email is properly authenticated.
- Start with None: Starting with p=none will allow monitoring before taking action.
Expert view
Expert from Word to the Wise shares the implication of using p=reject, noting it tells receivers to reject messages failing authentication. This requires ensuring your legitimate email is properly authenticated to prevent deliverability problems, highlighting the importance of monitoring and correctly configuring SPF and DKIM.
13 Jan 2022 - Word to the Wise
Expert view
Expert from Email Geeks shares a cautionary tale about a company (Crayola's parent company) that implemented 'p=reject' without proper support, guidance, or reporting, leading to deliverability issues.
17 Jun 2022 - Email Geeks
What the documentation says
4 technical articles
The documentation consistently explains that the DMARC 'p' tag dictates how recipient mail servers handle messages failing authentication. Options include 'none' (no action), 'quarantine' (mark as spam), and 'reject' (block). 'p=reject' provides the strongest anti-spoofing protection by instructing servers to reject failing emails, but necessitates careful monitoring to avoid unintended blocking of legitimate mail. The RFC 7489 provides the official specification. DMARC records can include 'rua' and 'ruf' for reporting.
Key findings
- P Tag Definition: The DMARC 'p' tag defines the policy for handling emails that fail DMARC checks.
- Reject Action: 'p=reject' instructs recipient servers to reject unauthenticated emails.
- Strongest Protection: 'p=reject' provides the strongest level of protection against spoofing.
- Official Specification: RFC 7489 formally defines the DMARC standard and the 'p' tag's values.
Key considerations
- Monitoring Required: Using 'p=reject' requires careful monitoring to avoid blocking legitimate emails.
- Potential for Blocking: Incorrect configuration can lead to legitimate emails being rejected.
- Reporting Tags: 'rua' and 'ruf' tags are important for receiving reports on DMARC results.
Technical article
Documentation from DMARC.org explains that using 'p=reject' instructs recipient mail servers to reject emails that fail DMARC authentication. This provides the strongest level of protection against spoofing but requires careful monitoring to avoid blocking legitimate email.
30 Mar 2025 - DMARC.org
Technical article
Documentation from RFC 7489, the official DMARC specification, formally defines the 'p' tag and its possible values ('none', 'quarantine', 'reject'), detailing the expected behavior of receiving mail servers for each policy option. This is the definitive source for understanding DMARC policy implementation.
28 Jun 2022 - RFC Editor
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