SPF Record CheckerValidate Email Authentication

Check SPF records to validate authorized mail servers, detect syntax errors, and get recommendations for improving email deliverability.

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SPF Record Validation

SPF (Sender Policy Framework) records prevent email spoofing by defining which mail servers are authorized to send email on behalf of your domain. A valid SPF record starts with v=spf1 and includes mechanisms that specify authorized sources.

SPF Mechanisms Explained

include: References another domain's SPF record. Example: include:_spf.google.com authorizes Google Workspace mail servers.

ip4/ip6: Explicitly authorizes specific IP addresses or ranges. Example: ip4:192.0.2.0/24 authorizes an entire subnet.

a/mx: Authorizes mail servers listed in A or MX records. Simple but may cause unnecessary DNS lookups.

Qualifiers: -all (hard fail, reject), ~all (soft fail, mark suspicious), +all (pass all, insecure).

Common SPF Issues

Too Many DNS Lookups: SPF is limited to 10 DNS lookups. Each include: counts as one lookup. Exceeding this limit causes SPF validation to fail entirely. Solution: flatten your SPF record by replacing includes with explicit IP ranges.

Multiple SPF Records: Only one SPF record is allowed per domain. Having multiple TXT records starting with v=spf1 causes all to be ignored. Merge them into a single record.

Weak Qualifiers: Using ?all (neutral) or +all (pass all) provides no protection. Use ~all for testing or -all for strict enforcement.

Missing SPF Record: Without an SPF record, recipients cannot validate your mail servers, increasing the likelihood of emails being marked as spam.

SPF Best Practices

Start with a monitoring policy (~all) and review email logs for legitimate sources being blocked. Gradually tighten to -all once confident in your configuration.

Keep your SPF record under 255 characters and minimize DNS lookups by using IP ranges instead of includes when possible. Document all authorized mail sources to prevent accidental blocking during updates.

Combine SPF with DMARC and DKIM for comprehensive email authentication. SPF alone is insufficient—DMARC policies enforce SPF results and provide visibility into authentication failures.

FAQ

What is an SPF record?▸
SPF (Sender Policy Framework) is a DNS TXT record that lists which mail servers are authorized to send email on behalf of your domain. It helps prevent email spoofing and improves deliverability.
What does v=spf1 mean?▸
v=spf1 identifies the record as an SPF version 1 record. All SPF records must start with this prefix. The remainder of the record defines authorized mail servers and the policy for handling failures.
How do I fix SPF too many lookups error?▸
SPF is limited to 10 DNS lookups. Replace include: mechanisms with explicit IP ranges when possible. For complex setups, consider SPF flattening services or split mail domains across subdomains with separate SPF records.
Should I use -all or ~all?▸
Use ~all (soft fail) during testing to mark suspicious emails without blocking them. Once confident in your configuration, upgrade to -all (hard fail) to instruct recipients to reject unauthorized mail. Never use +all which provides no protection.
Why is my SPF record not working?▸
Common issues include exceeding 10 DNS lookups, having multiple SPF records (only one allowed), syntax errors, or missing mail servers in your SPF record. Use this tool to identify specific issues and get remediation recommendations.
Do I need SPF if I have DMARC?▸
Yes. DMARC relies on SPF and DKIM for authentication. DMARC defines policies for handling authentication failures but requires at least one of SPF or DKIM to pass. Implement both SPF and DKIM with DMARC for best protection.