Definition
SPF (Sender Policy Framework, RFC 7208) is a TXT record on your domain that lists the servers and services allowed to send mail using that domain in the envelope sender (the return path). Receiving servers compare the connecting IP address against your record.
A typical record for a domain using Google Workspace and one marketing platform:
v=spf1 include:_spf.google.com include:sendgrid.net ~all
include: pulls in another domain's list of IPs. The final all term says what to do with everything else: -all means fail, ~all means soft fail (accept but treat as suspicious).
Why it matters
SPF is part of the authentication Gmail and Yahoo require. Since February 2024, every sender to Gmail needs SPF or DKIM, and bulk senders need SPF, DKIM and DMARC. Microsoft announced similar requirements for high-volume senders to Outlook.com in 2025.
SPF on its own has two well-known weak spots. It checks the envelope sender, not the From address people see, which is why DMARC adds alignment. And it breaks on forwarding, because the forwarding server's IP is not in your record.
Common mistakes:
- Two SPF records. A domain may publish only one. Two records make SPF fail. Merge them.
- Too many lookups. SPF allows at most 10 DNS lookups while evaluating a record. Each
include,a,mxandredirectcounts, including nested ones. Past 10, the result is a permanent error. - Forgetting a tool. Every service that sends as your domain, such as a CRM, help desk or sequencer, needs to be covered.
How SimpleCold handles it
SPF is about your sending side, so it does not change whether a recipient's address is valid. SimpleCold verifies the people you are emailing. To check your own record, including the lookup count, use the free SPF checker.