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Summary

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a critical email authentication protocol that helps protect domain owners from email spoofing and phishing. Understanding how DMARC policies apply to both organizational (root) domains and their associated subdomains is crucial for comprehensive email security and deliverability. By default, a DMARC policy set for an organizational domain will apply to all its subdomains, unless a specific DMARC record is published for a particular subdomain.

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What email marketers say

Email marketers often navigate the complexities of DMARC policies, especially when managing multiple sending domains and subdomains for various campaigns, such as transactional emails, marketing newsletters and operational communications. Their primary concern is ensuring emails reach the inbox while protecting brand reputation and preventing abuse. Understanding how DMARC works with domains and subdomains is key for effective email marketing.

Marketer view

Email marketer from Email Geeks explains that if DMARC is set for the organizational domain, it applies to all mail from that domain and any subdomains without their own records. If it is set at the subdomain, it will only apply to that specific subdomain, providing targeted control.

15 May 2019 - Email Geeks

Marketer view

Email marketer from Email Geeks points out the utility of the sp= tag in the DMARC record at the organizational domain, allowing for distinct policies for it and its subdomains, which is often useful for varied email strategies.

15 May 2019 - Email Geeks

What the experts say

Deliverability experts emphasize strategic DMARC implementation for organizational domains and subdomains to achieve robust email security and optimal inbox placement. Their insights often delve into the nuances of policy application, the use of the sp tag, and the importance of data-driven policy progression.

Expert view

Deliverability expert from SpamResource observes that careful planning is required when implementing DMARC across multiple subdomains, particularly when different subdomains handle distinct types of email traffic, to ensure consistent policy application.

22 Mar 2024 - SpamResource

Expert view

Deliverability expert from Word to the Wise suggests that an organizational DMARC record provides a baseline of protection, but specific subdomain policies (using sp) can fine-tune security measures for critical sending streams without needing separate comprehensive records for each.

22 Mar 2024 - Word to the Wise

What the documentation says

Official documentation and technical specifications for DMARC, such as RFCs and industry standards, define how DMARC policies interact with organizational domains and subdomains. They provide the foundational rules for DMARC record publication, policy inheritance, and the role of specific tags like sp, which are crucial for consistent implementation across the email ecosystem.

Technical article

Technical documentation from DuoCircle states that the DMARC sp tag (subdomain policy) allows domain owners to specify how DMARC should manage illegitimate emails sent from their subdomains, providing granular control over policy inheritance.

23 Apr 2024 - DuoCircle

Technical article

Technical documentation from VerifyDMARC explains that a DMARC DNS record applied to a domain will also affect any subdomains, unless a subdomain has its own DMARC DNS record, in which case the subdomain's specific policy takes precedence.

08 Apr 2024 - VerifyDMARC

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