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Subdomain delegation for email vendors checklist for 2026

Short answer

A complete subdomain delegation for email vendors checklist has 4 setup items and 2 things to audit against. Work through setup in order, then schedule a quarterly review.

Setup checklist#

  • ☐ 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.

Audit checklist#

  • ☐ Confirm you are not: delegating the whole zone to a vendor via NS records, giving them control over more than mail.
  • ☐ Confirm you are not: forgetting sp= in DMARC, leaving delegated subdomains unenforced.

Ongoing monitoring#

  • ☐ Weekly: review provider dashboards (Postmaster Tools, SNDS) and bounce logs
  • ☐ Monthly: re-run the setup verification after any vendor or DNS change
  • ☐ Quarterly: full audit against this checklist

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.

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