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How should I configure DMARC for multiple domains and when should I implement a reject policy?

Summary

Configuring DMARC for multiple domains requires a clear understanding of how DMARC works and a careful, phased approach to policy implementation. Each domain from which you send email, including subdomains, needs its own DMARC record to ensure proper authentication and policy enforcement. The transition to a reject policy, while offering the strongest protection against spoofing and brand abuse, must be executed meticulously to avoid disrupting legitimate email flows. This involves extensive monitoring of DMARC reports at the 'none' and 'quarantine' policy stages.

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What email marketers say

Email marketers often approach DMARC implementation with practical concerns about deliverability and the impact on their sending infrastructure. Their focus typically revolves around ensuring that legitimate emails reach the inbox while also safeguarding their brand from abuse. The journey from a 'p=none' to a 'p=reject' policy is seen as a cautious progression, driven by the desire for enhanced security without unintended mail disruptions.

Marketer view

An email marketer from Email Geeks confirms the necessity of setting up DMARC policies for each domain from which emails are intended to be sent, especially when planning to move to a reject policy. This ensures comprehensive coverage across all email-sending identities.

05 Feb 2020 - Email Geeks

Marketer view

A marketer from Mailgun's blog emphasizes that a DMARC reject policy instructs Internet Service Providers (ISPs) to automatically reject emails from fraudulent IPs attempting to use your domain. This serves as a strong defense against unauthorized use.

22 Jun 2023 - Mailgun

What the experts say

Deliverability experts emphasize the precision required for DMARC implementation, particularly when dealing with multiple domains and the transition to a reject policy. Their advice centers on rigorous data analysis, understanding the specific impact of DMARC on various email streams, and managing expectations regarding its role in combating different types of email fraud. They stress that DMARC is a powerful tool for domain authentication and brand protection, but it's not a silver bullet for all email security concerns.

Expert view

A deliverability expert from Email Geeks clarifies that DMARC primarily focuses on the domain found in the 'From:' header field, emphasizing that each email stream originating from different domains should be managed independently. This approach ensures accurate policy application.

05 Feb 2020 - Email Geeks

Expert view

A deliverability expert from SpamResource suggests that the ideal monitoring period before moving to a stricter DMARC policy depends on the complexity and age of the email infrastructure, as well as the resources dedicated to resolving authentication issues. This is not a one-size-fits-all scenario.

10 Apr 2024 - SpamResource

What the documentation says

Official documentation and technical guides provide the foundational rules and recommended practices for DMARC configuration and policy deployment. They outline the strict requirements for SPF and DKIM alignment, the meaning of various DMARC tags, and the intended behavior of 'none,' 'quarantine,' and 'reject' policies. These resources serve as the authoritative source for understanding DMARC mechanics and ensuring compliant implementation across diverse sending environments.

Technical article

Documentation from Mailgun states that a DMARC policy instructs ISPs to reject emails from fraudulent IPs attempting to use your domain. This mechanism acts as a robust defense against email spoofing and enhances trust in your domain.

22 Jun 2023 - Mailgun

Technical article

DuoCircle documentation on DMARC policies indicates that the 'reject' policy helps instruct receiving servers to discard emails sent from your domain that fail DMARC authentication. This is crucial for domains aiming for maximum protection.

15 Nov 2024 - DuoCircle

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