Invalid SPF Record

Severity: Critical

What is SPF?

SPF (Sender Policy Framework) is an email authentication method that helps prevent email spoofing. It works by allowing domain owners to publish a DNS TXT record that specifies which mail servers are authorized to send email on behalf of their domain.

When someone receives an email claiming to be from example.com, their mail server looks up the SPF record for example.com and checks whether the sending server's IP address is listed as authorized. If it isn't, the email may be rejected or marked as spam.

An SPF record looks something like this:

v=spf1 include:_spf.google.com ip4:203.0.113.0/24 -all

This says: "Only Google's mail servers and the IP range 203.0.113.0/24 are allowed to send email for this domain. Reject everything else."

Why this is a problem

An invalid SPF record means the record contains syntax errors, unrecognized mechanisms, or malformed values. When an SPF record is invalid, receiving mail servers may not be able to parse it at all, which can lead to:

• Legitimate emails being rejected or sent to spam
• No SPF protection whatsoever, leaving the domain open to spoofing
• Unpredictable behavior across different mail providers

What you should do

• Review the SPF record for syntax errors — common mistakes include typos in mechanisms, missing colons, or extra spaces
• Validate the record using an SPF validation tool
• Ensure the record starts with v=spf1 (exactly, with no variations)
• Check that all include:, ip4:, ip6:, and a: mechanisms are correctly formatted
• Make sure there is only one SPF record per domain — multiple SPF records are invalid
• End the record with a catch-all mechanism like -all or ~all