Gmail enforces bulk-sender rules: authentication, one-click unsubscribe, and spam-rate thresholds under 0.3% in Postmaster Tools.
What subdomain delegation for email vendors are#
Subdomain delegation gives each third-party sender its own subdomain (for example news.example.com for the ESP, help.example.com for the helpdesk) with dedicated SPF, DKIM, and DMARC records, so each vendor's reputation and configuration are isolated.
Why it matters#
One SPF record cannot hold every vendor without exceeding the lookup limit, and one shared domain means one vendor's mistakes damage everyone's placement.
Setting up subdomain delegation for email vendors for Gmail#
- List every vendor that sends as your brand.
- Assign each a subdomain and delegate DNS or publish its records directly.
- Publish SPF and DKIM per subdomain using the vendor's values.
- Set the organizational DMARC record with sp= to cover all subdomains.
How Gmail reports results#
Open a delivered test message in Gmail and view the original or headers. Look for Authentication-Results and any provider-specific verdict headers. Use the provider's sender dashboard for aggregate reputation.
Common mistakes#
- Delegating the whole zone to a vendor via NS records, giving them control over more than mail.
- Forgetting sp= in DMARC, leaving delegated subdomains unenforced.
Frequently asked questions#
Does using a subdomain hurt brand recognition?
The visible From can still show your brand name; recipients rarely notice the subdomain, and providers reward the isolation.
Does Gmail require subdomain delegation for email vendors?
Gmail enforces bulk-sender rules: authentication, one-click unsubscribe, and spam-rate thresholds under 0.3% in Postmaster Tools. Treat subdomain delegation for email vendors as required for any meaningful volume.