SPF (Sender Policy Framework)
A DNS record that specifies which mail servers are authorized to send email on behalf of your domain.
What is SPF?
SPF, or Sender Policy Framework, is an email authentication standard that allows domain owners to declare which mail servers are permitted to send email using their domain name. It works by publishing a specially formatted TXT record in your domain’s DNS settings. When a receiving mail server gets a message claiming to be from your domain, it looks up your SPF record and checks whether the sending server’s IP address is on the approved list.
How SPF Works
When you send an email, the receiving server extracts the domain from the envelope sender address (the Return-Path header) and performs a DNS lookup for that domain’s SPF record. The SPF record contains a list of authorized IP addresses, IP ranges, and references to other domains whose SPF records should also be included. The receiving server compares the connecting IP address against this list and returns one of several results: pass, fail, softfail, or neutral.
A typical SPF record looks like this: v=spf1 include:_spf.google.com include:sendgrid.net -all. This tells receivers that Google’s mail servers and SendGrid’s servers are authorized senders, and all other sources should be rejected.
Why SPF Matters for Cold Email
Without a valid SPF record, your emails are far more likely to be flagged as spam or rejected outright. Major email providers like Gmail, Outlook, and Yahoo all check SPF as part of their filtering decisions. For cold email senders, SPF is table stakes. It is the first layer of authentication that proves you have legitimate control over the domain you are sending from.
Common Mistakes
The most frequent SPF error is exceeding the 10 DNS lookup limit. Every include mechanism in your SPF record counts as a lookup, and if you chain too many services together, your record becomes invalid. Another common issue is using ~all (softfail) instead of -all (hardfail), which sends a weaker signal to receivers. For cold email infrastructure, always use -all once you are confident your authorized senders are correctly listed.
Outspun & SPF
With Outspun’s managed infrastructure plans, SPF records are configured automatically for every domain we provision. No manual DNS editing required — we handle SPF, DKIM, and DMARC from day one so your sending domains pass authentication checks out of the box.
Keep learning
DKIM (DomainKeys Identified Mail)
An email authentication method that uses cryptographic signatures to verify that an email was sent by the domain it claims to be from.
DMARC (Domain-based Message Authentication, Reporting and Conformance)
An email authentication protocol that builds on SPF and DKIM to give domain owners control over what happens to unauthenticated email.
Need help with SPF (Sender Policy Framework)?
Outspun handles it for you. Managed email infrastructure with everything configured and monitored.