What is SPF (Sender Policy Framework)?
SPF is a DNS record that lists which servers are allowed to send email for a domain, so a receiving server can check that a message came from one of them.
Also called: SPF record.
An SPF record is a TXT record at the domain that starts with v=spf1 and lists mechanisms such as include:, a, mx and ip4:, ending in a rule for everything else (-all to fail it, ~all to soft-fail it). A domain should publish exactly one SPF record; two records is an error.
The SPF standard caps the DNS lookups a receiver will make while evaluating the record at 10. Each include, a, mx, ptr, exists and redirect counts, including the ones inside included records. Past 10, SPF returns a permanent error and the mail fails SPF, which is a common reason a domain with several sending tools breaks.
Google's guidelines for senders of more than 5,000 messages a day to Gmail require SPF and DKIM, plus a DMARC record and From: domain alignment with SPF or DKIM. Gmail began rejecting non-compliant traffic outright in November 2025, and Yahoo's rules mirror Google's.
The free SPF, DMARC and MX checker makes live DNS lookups for a domain, counts SPF lookups across includes, and gives a yes or no against those rules.