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Senddio glossary · Sender Policy Framework

What is SPF?

SPF authorises sending IPs for an envelope-sender or HELO domain. Receivers compare the connecting IP against that domain’s SPF record; SPF alone does not authenticate the visible From address.

How SPF works in plain English

Publish one SPF TXT record at the domain used by your envelope sender. Receivers evaluate the connecting IP against its mechanisms. A passing SPF result contributes to DMARC only when the authenticated domain aligns with the visible From domain.

Why SPF matters

SPF helps receivers evaluate whether an IP is authorised for the envelope-sender domain. Use it with aligned DKIM and DMARC to protect the visible From identity.

What does an SPF record look like?

An example is v=spf1 include:spf.senddio.com ~all. Merge the include required by your setup into your existing SPF record rather than publishing a second SPF record. A trailing -all produces an SPF fail for unmatched senders; it does not itself mandate rejection.

SPF lookup limit

SPF limits DNS-querying terms, including nested includes, to ten during evaluation. Check the complete include chain for every provider; a single include is not a guarantee that you remain below the limit.

Related terms
DKIM DMARC
FAQ

SPF — FAQ

No, but they work together. SPF authorises which servers may send on your behalf. DKIM signs the messages themselves so the contents can be verified. You need both, plus DMARC.

No. A domain may only publish one SPF record. If you need to authorise multiple providers, combine them into one record using includes.

Senddio shows the SPF include needed for your configuration. Merge it into the existing record and verify the result, including the DNS-lookup budget of any nested includes.

Senddio handles the boring parts of SPF for you.

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