Do subdomains need their own DMARC records if the main domain has one?
Summary
What email marketers say6Marketer opinions
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.
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.
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.
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.
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.
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.
What the experts say4Expert opinions
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.
Expert from Email Geeks explains that if the main domain has a DMARC entry, subdomains don't necessarily need separate entries.
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.
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.
What the documentation says4Technical articles
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.
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.
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.
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.