How does primary domain authentication affect subdomain deliverability and compliance?
Summary
What email marketers say8Marketer opinions
Email marketer from Mailjet shares that subdomains have their own reputation, separate from the primary domain. Poor sending practices on a subdomain can negatively impact its deliverability without directly affecting the primary domain's reputation, although the reverse is true when bad behaviour is on the primary domain.
Email marketer from Reddit explains that a DMARC policy on the primary domain can affect subdomains, depending on the policy's configuration (specifically, the `sp` tag for subdomain policy). A strict DMARC policy on the primary domain can cause deliverability issues for subdomains that don't have their own DMARC records.
Marketer from Email Geeks shares that compliance is always calculated for the organizational domain, and showing the subdomain is to help understand if the problem is in your subdomain or in another subdomain (or the organizational domain). Also notes that if your subdomain is all good, but the organizational domain is not - then the subdomain might still see enforcement.
Email marketer from GlockApps explains that monitoring the deliverability of subdomains separately from the main domain is essential. It ensures any deliverability issues with your primary domain aren't caused by something happening in a subdomain.
Email marketer from Postmark shares that if subdomains send significantly different types of email (e.g., marketing vs. transactional), using separate IPs for each can help isolate reputation and prevent deliverability issues. This segregation ensures that problems on one subdomain don't automatically impact the others.
Email marketer from StackExchange answers that generally, authentication settings (SPF, DKIM, DMARC) are not automatically inherited by subdomains. Each subdomain typically needs its own authentication records set up to ensure deliverability and compliance.
Email marketer from SparkPost explains that SPF records must be created for each subdomain sending mail to ensure proper authentication. Without a valid SPF record, emails from a subdomain are more likely to be marked as spam.
Email marketer from EmailVendorSelection shares that sender reputation is linked to both the domain and the IP address. Sending from a subdomain with poor authentication can negatively impact your overall sender reputation, especially if it shares an IP with the primary domain.
What the experts say6Expert opinions
Expert from Spam Resource explains that subdomains should have their own authentication records to avoid deliverability issues. If the primary domain fails authentication, subdomains may be impacted depending on the DMARC policy and sender reputation.
Expert from Email Geeks suggests that a spam spike could be due to a test where the mail went out of spam into the inbox for that day, and people saw mail they hadn't seen because it was going to spam and they immediately reacted negatively to it.
Expert from Email Geeks shares she is confused about what "in compliance" means and what the impact is, adding that she currently has a client who is not "in compliance" with List-Unsubscribe but their deliverability is just fine.
Expert from Email Geeks suggests focusing on getting complaints down first, as that strikes her as much more impactful for delivery.
Expert from Word to the Wise shares that a strong DMARC policy (e.g., reject or quarantine) on the organizational domain will apply to subdomains, unless a specific subdomain policy (`sp`) is defined. If the subdomains aren't properly authenticated, email can be blocked or sent to spam.
Expert from Spam Resource explains the importance of configuring SPF records for all subdomains that send email. Failure to do so can lead to authentication failures and negatively impact deliverability, as mail servers will not be able to verify the legitimacy of the sender.
What the documentation says5Technical articles
Documentation from DMARC.org explains that DMARC has specific policies that can be applied to subdomains. The subdomain policy (`sp`) tag in a DMARC record allows domain owners to specify how DMARC should handle authentication failures on subdomains.
Documentation from Google Workspace Admin Help explains that delegating a subdomain involves creating DNS records that point to Google's servers. Properly delegating subdomains is crucial for ensuring emails are correctly routed and authenticated.
Documentation from RFC Editor explains that SPF records are evaluated independently for each domain and subdomain. A subdomain does not inherit the SPF record of its parent domain unless explicitly included.
Documentation from Microsoft Learn explains that DKIM signatures should be set up for both the primary domain and any subdomains used for sending email. Correct DKIM implementation helps ensure that emails from subdomains are properly authenticated.
Documentation from Valimail shares how a properly implemented DMARC record, including subdomain policy, ensures that unauthorized use of subdomains is prevented. It's important to monitor and enforce DMARC records on all sending domains and subdomains.