Do subdomains need their own DMARC records if the main domain has one?

Summary

While a DMARC record at the organizational domain level *can* cover subdomains, the consensus is that implementing individual DMARC records for each subdomain is highly recommended. This allows for more granular control over email policies, enhanced security to prevent spoofing, improved visibility and reporting on email traffic, easier identification of issues, and a more nuanced approach to managing email authentication. Furthermore, setting up DMARC records for subdomains that don't send email can explicitly prevent spammers from exploiting them. Ultimately, the best practice depends on the specific needs and security requirements of each organization, but proactively managing DMARC at the subdomain level is generally considered a more robust approach.

Key findings

  • Main Domain Coverage (Possible): The organizational domain's DMARC record *can* cover subdomains if no subdomain policy is defined.
  • Individual Records (Recommended): Implementing individual DMARC records for each subdomain is *highly recommended*.
  • Granular Control: Subdomain DMARC records enable more granular control over email policies.
  • Enhanced Security: Subdomain DMARC records enhance security by preventing spoofing and unauthorized email sending.
  • Improved Reporting: Individual records allow for detailed reporting on email traffic from each subdomain.
  • Issue Identification: Individual records simplify identifying and resolving issues specific to each subdomain.
  • Explicit Prevention: DMARC records can explicitly prevent email sending from subdomains that should not be sending email.

Key considerations

  • Specific Policy Needs: Determine if different subdomains require specific DMARC policies based on their function and email practices.
  • Reporting Requirements: Assess whether you need separate reporting for each subdomain to effectively monitor email activity and potential abuse.
  • Security Level: Consider the desired level of security for each subdomain and whether individual records are necessary to achieve that level.
  • Management Overhead: Balance the benefits of granular control with the potential increase in complexity and management overhead.
  • ISP Compatibility: Consider that implementing separate records reduces the possibility of deliverability issues with some ISPs

What email marketers say
6Marketer opinions

While a DMARC record at the organizational domain can cover subdomains, it's generally recommended to implement DMARC records for each subdomain. This approach provides greater control, improved visibility, and enhanced security, especially when subdomains have distinct sending purposes, differing reputation needs, or if you want to explicitly prevent email sending from certain subdomains. Individual records enable more granular policies and better reporting capabilities.

Key opinions

  • DMARC Coverage: A DMARC record on the main domain can cover subdomains.
  • Granular Control: Individual subdomain DMARC records offer better control and visibility.
  • Enhanced Security: Subdomain DMARC records enhance security by controlling email sending policies.
  • Prevent Spoofing: DMARC records can explicitly prevent email sending from specific subdomains.
  • Improved Reporting: Individual DMARC records enable granular reporting for each subdomain.

Key considerations

  • Subdomain Purpose: Consider the specific purpose of each subdomain when deciding whether to implement individual DMARC records.
  • Reputation Needs: Evaluate whether subdomains have distinct reputation needs that warrant separate DMARC policies.
  • Reporting Requirements: Assess whether you require detailed reporting on email activity from individual subdomains.
  • Security Level: Determine the desired level of security and control for email authentication across your domains.
  • Maintenance Overhead: Balance the benefits of individual records against the increased complexity of managing multiple DMARC policies.
Marketer view

Email marketer from EasyDMARC states that implementing DMARC on subdomains is optional, but is a recommended approach. It allows for more granular control, and better reporting capabilities.

September 2021 - EasyDMARC
Marketer view

Email marketer from Mailhardener explains that while a general DMARC record might suffice, more secure setups can make subdomains much safer by actively declaring which can or cannot send emails through specific policies.

April 2022 - Mailhardener
Marketer view

Marketer from Email Geeks explains that a DMARC record at the org domain can cover all subdomains as long as no subdomain needs its own policy or reporting.

March 2022 - Email Geeks
Marketer view

Email marketer from StackExchange shares that it is better to have a DMARC record for each subdomain. If a subdomain never sends mail a record can be setup to explicitly prevent mail from being sent from the subdomain.

March 2023 - StackExchange
Marketer view

Email marketer from EmailSecurityFAQ explains that it is not strictly necessary for subdomains to have their own DMARC records if the main domain has one, but it is highly recommended for better control and visibility, especially if subdomains handle different types of email traffic.

March 2024 - EmailSecurityFAQ
Marketer view

Email marketer from Reddit explains that while not always mandatory, having individual DMARC records for subdomains provides better control, especially if subdomains have different sending purposes or reputation needs.

December 2023 - Reddit

What the experts say
4Expert opinions

While a DMARC record on the main domain can sometimes suffice, it's generally beneficial to implement individual DMARC records for subdomains. This provides enhanced security, prevents spoofing, and offers greater control, particularly when you want to explicitly prevent email sending from a specific subdomain or ensure compatibility across different ISPs. If uncertain, adding a DMARC record for the subdomain is a safe practice.

Key opinions

  • Main Domain Coverage: A main domain DMARC record can sometimes cover subdomains.
  • Enhanced Security: Subdomain DMARC records enhance security and prevent spoofing.
  • Explicit Control: DMARC records allow you to explicitly prevent email from specific subdomains.
  • ISP Compatibility: Subdomain DMARC records may resolve compatibility issues with some ISPs.
  • When in doubt, add it: Adding a DMARC record for the subdomain will not hurt.

Key considerations

  • Security Needs: Evaluate the security needs of your subdomains and the risk of spoofing.
  • Control Requirements: Consider the level of control you need over email sending from each subdomain.
  • ISP Compatibility: Ensure compatibility with various ISPs to avoid deliverability issues.
  • Prevention of Spoofing: If there is a risk of spoofing from subdomains, DMARC records are necessary.
Expert view

Expert from Word to the Wise shares that implementing DMARC policies on subdomains enhances security by providing greater control over email authentication, as well as helping to identify and prevent spoofing attempts.

January 2022 - Word to the Wise
Expert view

Expert from Email Geeks explains that if the main domain has a DMARC entry, subdomains don't necessarily need separate entries.

January 2025 - Email Geeks
Expert view

Expert from Spam Resource explains that if you don't want people sending email from a subdomain, you should set up a DMARC record for the subdomain that says not to. This is to prevent spammers from using your subdomain to send email.

September 2023 - Spam Resource
Expert view

Expert from Email Geeks shares that when in doubt, add a DMARC record for the subdomain. It won’t make things worse and might solve issues with some ISPs.

July 2024 - Email Geeks

What the documentation says
4Technical articles

DMARC policies apply to subdomains if no specific policy is defined for them. Although the main domain's DMARC record can cover subdomains, creating individual DMARC records for each subdomain is highly recommended for better control, more granular policies, enhanced reporting, and easier issue identification. Implementing individual DMARC records allows for a more nuanced approach and optimizes email security.

Key findings

  • Inherited Policy: Subdomains inherit the DMARC policy of the organizational domain if they lack an explicit DMARC record.
  • Granular Control: Specific DMARC records for subdomains enable more granular control over email policies.
  • Enhanced Reporting: Individual DMARC records allow for detailed reporting for each subdomain.
  • Easier Identification: Individual records simplify identifying and addressing email issues specific to each subdomain.
  • Nuanced Approach: Implementing DMARC records in subdomains helps a nuanced approach to email security.

Key considerations

  • Policy Specificity: Consider whether you need specific DMARC policies for different subdomains based on their function.
  • Reporting Needs: Evaluate if you require separate reporting for each subdomain to monitor email activity effectively.
  • Security Requirements: Assess the level of security needed for each subdomain and whether it warrants a distinct DMARC policy.
  • Complexity Management: Balance the benefits of granular control with the increased complexity of managing multiple DMARC records.
  • Implementation Effort: Assess resources needed to create, implement and monitor individual DMARC records for multiple subdomains.
Technical article

Documentation from Cloudflare explains that for best results, implement individual DMARC records for each subdomain. This allows a nuanced approach with different policies for each, and makes it easier to identify issues.

March 2022 - Cloudflare
Technical article

Documentation from DMARC.org shares that subdomains inherit the DMARC policy of the organizational domain unless they have their own explicit DMARC record. If a subdomain sends email, it is highly recommended to have a DMARC record for that subdomain.

January 2023 - DMARC.org
Technical article

Documentation from Microsoft Learn notes that while a DMARC record at the organizational domain level can cover subdomains, creating specific DMARC records for each subdomain allows for more granular control and reporting.

November 2023 - Microsoft Learn
Technical article

Documentation from Google Workspace Admin Help explains that a DMARC policy applies to subdomains if a subdomain policy isn't defined. If you want to define specific DMARC policies for subdomains, you need to add DMARC records for those subdomains.

March 2024 - Google Workspace Admin Help