Summary
Learning about DMARC involves understanding its role in email authentication, leveraging various resources including M3AAWG training, dmarc.org, and documentation from Google, Microsoft, and the IETF. DMARC builds upon SPF and DKIM to prevent spoofing and phishing, enabling senders to specify how recipients should handle unauthenticated email. Key aspects include configuring SPF and DKIM, carefully choosing and implementing DMARC policies (starting with 'p=none' for monitoring), analyzing DMARC reports, and understanding how DMARC records are structured. Considerations should include the impact of email forwarding on SPF, and the importance of a gradual rollout to avoid disrupting legitimate email flow. Advanced configurations include DANE for increased security.
Key findings
- DMARC Authentication: DMARC utilizes SPF and DKIM to authenticate emails and provides instructions to receiving servers on handling unauthenticated messages.
- Spoofing Prevention: DMARC's primary function is to prevent domain spoofing and phishing attacks by enforcing policies on unauthenticated email.
- SPF/DKIM Reliance: DMARC relies on properly configured SPF and DKIM records to function effectively.
- Report Analysis: Analyzing DMARC reports is crucial for identifying authentication failures and refining DMARC policies.
- Policy Enforcement: Gradually transitioning to stricter DMARC policies (quarantine, reject) reduces spoofing attempts.
Key considerations
- SPF/DKIM Configuration: Ensure SPF and DKIM are correctly set up before implementing DMARC.
- Gradual Rollout: Implement DMARC policies gradually to avoid blocking legitimate email.
- Report Monitoring: Regularly monitor DMARC aggregate and forensic reports to identify and address authentication issues.
- Forwarding Impact: Be aware that email forwarding can break SPF and lead to DMARC failures.
- Understanding Sender Practices: Thoroughly understand existing email sending practices to implement appropriate policies.
What email marketers say
12 marketer opinions
Learning and understanding DMARC involves grasping its role in email authentication and deliverability. DMARC leverages SPF and DKIM to verify email authenticity and allows domain owners to specify how recipient mail servers should handle unauthenticated emails. Crucial aspects include understanding DMARC reports (both aggregate and forensic), implementing the appropriate DMARC policy (starting with 'p=none' for monitoring), and correctly setting up DMARC records with proper syntax and semantics. Resources like learndmarc.com, kickbox blog, and EasyDMARC provide valuable insights. Understanding alignment modes and the interaction between DMARC, SPF, and DKIM is also vital for effective implementation.
Key opinions
- DMARC Function: DMARC relies on SPF and DKIM to authenticate emails and instructs receiving servers on how to handle messages that fail authentication.
- Policy Implementation: Start with a 'p=none' policy to monitor email traffic and identify legitimate sending sources before moving to stricter policies.
- Reporting Importance: DMARC reports are crucial for understanding how email is being handled, identifying authentication failures, and adjusting DMARC policies.
- Record Configuration: A DMARC record is a TXT record in DNS that includes essential tags like 'v,' 'p,' 'rua,' and 'ruf,' requiring precise configuration.
- SPF/DKIM Dependence: DMARC builds upon SPF and DKIM, and those protocols must be configured correctly for DMARC to function effectively.
Key considerations
- Policy Selection: Carefully choose the DMARC policy ('none,' 'quarantine,' or 'reject') based on your understanding of your email ecosystem.
- Report Monitoring: Regularly monitor DMARC aggregate and forensic reports to identify and address authentication issues and potential threats.
- Alignment Modes: Consider DMARC alignment modes (strict or relaxed) to ensure that SPF and DKIM authentication results align with the domain in the From address.
- SPF Forwarding Issues: Be aware of how forwarding can break SPF which is a cause of DMARC failures.
- Gradual Enforcement: Implement a DMARC policy in stages so legitimate email isn't inadvertently blocked during the enforcement process.
Marketer view
Email marketer from Postmark explains that DMARC relies on SPF and DKIM to verify the authenticity of email messages. SPF verifies the sending server's IP address, while DKIM uses cryptographic signatures to ensure message integrity. DMARC builds on these mechanisms to provide a unified authentication framework.
13 Feb 2022 - Postmark
Marketer view
Email marketer from Mailjet shares that DMARC aggregate reports provide a summary of email authentication results, grouped by sending source and authentication status. These reports are sent daily and can be used to monitor email authentication performance over time.
18 Jun 2024 - Mailjet
What the experts say
4 expert opinions
Learning and understanding DMARC involves accessing publicly available training resources like the M3AAWG series on YouTube, recognizing that forwarded emails often break SPF and cause DMARC failures, and implementing DMARC gradually while carefully monitoring reports. It also requires understanding your existing sending practices to avoid disruption when transitioning to stricter DMARC policies. DMARC's strength lies in its ability to enforce policies on unauthenticated email, which significantly reduces spoofing and phishing.
Key opinions
- Training Resources: M3AAWG offers a publicly available training series on YouTube for learning about DMARC.
- Forwarding Issues: Forwarded email often breaks SPF, causing DMARC failures unless messages are rewritten to comply with SPF or DKIM.
- Gradual Implementation: A detailed approach to DMARC implementation involves understanding existing sending practices and gradually transitioning to stricter policies.
- Enforcement Power: DMARC's ability to enforce policies on unauthenticated email is crucial for reducing spoofing and phishing attacks.
Key considerations
- Existing Practices: Understand your current email sending practices before implementing DMARC to avoid unintended disruptions.
- Inventory Sources: Inventory all email sources within your organization before implementing DMARC.
- Report Monitoring: Carefully monitor DMARC reports during implementation to ensure legitimate email isn't inadvertently blocked.
- SPF Compliance: Ensure that email forwarding practices comply with SPF or DKIM to prevent DMARC failures.
Expert view
Expert from Word to the Wise shares a detailed approach to DMARC implementation, highlighting the importance of understanding existing sending practices, inventorying all email sources, and gradually transitioning to a stricter DMARC policy to minimize disruption and maximize email delivery.
26 Apr 2024 - Word to the Wise
Expert view
Expert from Word to the Wise responds that DMARC's power lies in its ability to enforce policies on unauthenticated email, which can significantly reduce spoofing and phishing attacks. A key aspect is careful monitoring of DMARC reports to ensure legitimate email isn't inadvertently blocked during the enforcement process.
23 Feb 2024 - Word to the Wise
What the documentation says
5 technical articles
Learning and understanding DMARC involves recognizing it as an email authentication protocol built upon SPF and DKIM. Its primary function is to enable senders and receivers to determine the legitimacy of an email and dictate actions for unauthenticated messages, thus preventing domain spoofing. Key resources include dmarc.org, Google Workspace Admin documentation, Microsoft documentation, RFC7489 (defining the DMARC standard), and IETF documentation which introduces opportunistic DANE as an additional layer of authentication alongside DMARC.
Key findings
- DMARC Definition: DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol.
- Functionality: DMARC helps senders and receivers verify email legitimacy and specifies how to handle unauthenticated messages.
- Spoofing Prevention: DMARC prevents spammers from spoofing domains by leveraging SPF and DKIM.
- Standard Definition: RFC7489 defines the DMARC standard, detailing authentication mechanisms and handling of failing messages.
- SPF/DKIM Integration: DMARC builds on SPF and DKIM, adding reporting and conformance mechanisms.
Key considerations
- Outbound Email Validation: DMARC is critical for validating outbound email to prevent spoofing and phishing.
- SPF/DKIM Configuration: Properly configure SPF and DKIM as prerequisites for effective DMARC implementation.
- DANE Integration: Consider opportunistic DANE as an additional layer of authentication alongside DMARC for enhanced security.
- Authentication Failure Handling: Define clear policies for how recipient email systems should handle messages that fail SPF or DKIM checks.
Technical article
Documentation from Microsoft explains DMARC is used to validate outbound email to prevent spoofing, and is one of three parts of email authentication (the other two are SPF and DKIM). DMARC's purpose is to indicate to recipient email systems what to do with messages that fail SPF or DKIM checks and are claimed to be from your organization's domain.
25 Mar 2025 - Microsoft
Technical article
Documentation from dmarc.org explains that DMARC, which stands for “Domain-based Message Authentication, Reporting & Conformance”, is an email authentication protocol. It builds on SPF and DKIM to add reporting, and allows domain owners to indicate how email receivers should handle messages that fail authentication.
18 Feb 2024 - dmarc.org
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