Glossary

SPF (Sender Policy Framework)

SPF is a DNS TXT record listing which servers may send email for your domain, helping receivers reject forged messages and spam.

SPF (Sender Policy Framework) is an email-authentication standard that lets a domain owner declare, via a txt-record, exactly which mail servers are permitted to send email on the domain's behalf.

How it works

The domain publishes a TXT record such as:

v=spf1 include:_spf.google.com ip4:203.0.113.5 ~all

A receiving server checks the sending IP against this list. The ~all (soft fail) or -all (hard fail) qualifier says what to do with mail from unlisted sources.

Limits to know

SPF allows a maximum of 10 DNS lookups; exceeding it causes failures.
It checks the envelope sender, not the visible From: header — which is why dmarc is needed to tie it together.

Why it matters for hosting

SPF is one leg of the spf/dkim/dmarc trio that protects your domain from spoofing and keeps legitimate mail out of spam folders. It must list every service that sends as your domain, including your host and any newsletters.

See also

DKIM (DomainKeys Identified Mail) DKIM cryptographically signs outgoing email so receivers can verify it truly came from your domain and was not altered in transit. DMARC DMARC builds on SPF and DKIM to tell receivers how to handle mail that fails authentication and sends you reports on abuse of your domain. TXT Record A TXT record stores arbitrary text in DNS, widely used for domain verification and email authentication policies like SPF, DKIM, and DMARC. MX Record An MX record is the DNS entry that directs a domain’s email to the correct mail servers, with priority values choosing primary and backups.

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