Glossary

SPF Record — What It Is and How to Fix It

An SPF (Sender Policy Framework) record is a DNS TXT record that lists which mail servers are authorized to send email on behalf of your domain. Receiving mail servers check your SPF record to verify that incoming email from your domain was sent by an authorized server — if the check fails, the email may be rejected or marked as spam.

How SPF Records Work

SPF works by publishing a list of authorized IP addresses and mail servers in your DNS. When an email arrives, the receiving server looks up your SPF record and checks whether the sending IP is on the list. The result is either pass, fail, softfail, or neutral.

The SPF 10-Lookup Limit

SPF records are limited to 10 DNS lookups during evaluation. Each include:, a:, and mx: mechanism triggers a lookup. Exceeding 10 lookups causes a PermError, which many receiving servers treat as a hard fail — causing your legitimate emails to bounce.

Common SPF Problems

• Too many include: statements (over 10 lookups)
• Multiple SPF records on the same domain
• Using +all instead of ~all or -all
• Missing include for a third-party sender like SendGrid or Mailgun

How to Check Your SPF Record

Use DomainPreflight's DNS Preflight tool to check your SPF record, count DNS lookups, and get a copy-paste fix.