SPF checker
Look up a domain's SPF record and see which mail servers it authorizes to send on the domain's behalf.
SPF lives as a TXT record on the domain itself, not a subdomain.
Enter a domain to check its SPF record
Authorized senders and the qualifier that decides what happens to everyone else.
SPF (Sender Policy Framework) is a TXT record published at a domain's apex that lists which mail servers are authorized to send email on its behalf. A receiving server checks the sending server's IP address against this list; any IP not listed is unauthorized, though the resulting action depends on the record's final qualifier.
The mechanism at the end of the record determines that outcome: -all hard-fails unauthorized senders, ~all soft-fails them (flagged as suspicious but not rejected outright), and +all, rarely used intentionally, authorizes any sender. A domain should publish exactly one SPF record. Publishing more than one is an explicit error under RFC 7208 and can cause mail to be rejected specifically because of the duplication.
SPF verifies only the sending server's IP address, not the message content or signature. That verification is performed by DKIM, which is why the two are typically used together.