SPF record checker

An SPF (Sender Policy Framework) record is a DNS TXT record that lists the mail servers authorised to send email on behalf of your domain. Receiving mail servers check this record to verify that incoming email claiming to be from your domain was sent by an authorised server. Without SPF, anyone can spoof your domain in the From address.

-all (hard fail) instructs receiving servers to reject any email not matching your SPF record. ~all (softfail) marks non-matching emails as suspicious but still delivers them. For production domains, -all is recommended once all your legitimate sending sources are added.

RFC 7208 limits SPF to 10 DNS lookups to prevent denial-of-service attacks and excessive DNS load. Each include, a, mx, ptr, and exists mechanism counts as one lookup. Exceeding 10 lookups causes a PermError, which effectively makes SPF fail for your domain.

No. Having more than one SPF (v=spf1) TXT record on your domain causes a PermError and breaks SPF authentication. If you need to authorise multiple senders, combine everything into a single SPF record using multiple mechanisms.

SPF alone is not enough. SPF only validates the envelope sender (the "Return-Path" address), not the visible "From" header. DMARC is required to connect SPF (and DKIM) validation to the From header and actually prevent spoofing of your visible sender address.