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
6 marketer 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.
24 Apr 2023 - 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.
14 Oct 2023 - Mailhardener
What the experts say
4 expert 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.
17 Nov 2024 - 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.
25 Jun 2022 - Email Geeks
What the documentation says
4 technical 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.
9 Jan 2025 - 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.
6 Aug 2024 - DMARC.org
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