Glossary
SPF (Sender Policy Framework)
A DNS-published policy in which a domain lists the hosts authorised to use its name in the SMTP MAIL FROM or HELO identity, so a receiving server can check whether the sending IP is allowed.
In plain terms
A public list of the servers permitted to send mail using your domain.
Why it matters for deliverability
SPF is one of the two mechanisms DMARC is built on, and it is the one that breaks silently when you add a new sending service and forget to update the record.
What to do about it
- Keep the record within the 10 DNS-lookup limit — exceeding it makes SPF fail, not degrade.
- Re-check the record every time you add an ESP, CRM or transactional provider.
- Remember SPF authenticates the envelope domain, so forwarding commonly breaks it.
Source
RFC 7208 — Sender Policy Framework (SPF) for Authorizing Use of Domains in Email
“ADministrative Management Domains (ADMDs) can explicitly authorize the hosts that are allowed to use their domain names, and a receiving host can check such authorization”
Checked 2026-08-29
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Definitions reviewed 2026-08-29. Spotted something wrong? Tell us.
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