SPF (Sender Policy Framework) — Sender Policy Framework
What is SPF (Sender Policy Framework)?
SPF (Sender Policy Framework) is a DNS record listing which mail servers are authorized to send email on behalf of a domain, letting a receiving mail server check whether an incoming message actually came from an approved source or is likely spoofed. A message sent from a server not listed in the domain's SPF record typically fails SPF authentication, which is one of the signals a DMARC policy and spam filter both weigh when deciding whether to deliver it.
More detail
An SPF record must list every legitimate sending source for a domain — including any third-party email or messaging platform used — since an omitted source will fail SPF even if the mail is entirely legitimate.
SPF alone doesn't survive email forwarding well, since a forwarded message appears to come from the forwarding server rather than the original authorized sender — this is one reason DKIM and DMARC exist alongside it.
Frequently asked
- What happens if I add a new email tool but forget to update SPF?
- Mail sent through that tool will fail SPF authentication since its sending server isn't listed in the domain's authorized-senders record, which can hurt deliverability or trigger a DMARC policy to quarantine or reject those messages.
- Does SPF alone guarantee my email won't be marked as spam?
- No — SPF is one authentication signal among several (alongside DKIM, sender reputation, and DMARC alignment) that receiving servers weigh together, so passing SPF helps but doesn't by itself guarantee inbox placement.
See also
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