spf.syntax Reviewed July 2026

Quick fix

Use the scanner evidence to identify the exact invalid token or duplicate modifier.

What this finding means

SecuTest parses the `v=spf1` version marker, supported mechanisms, qualifiers, and modifiers. It reports syntax errors before evaluating the policy further. A syntactically invalid record cannot provide reliable authorization.

Interpretation boundary Use the exact evidence in your report. SecuTest reports externally observable conditions; it does not assume ownership, exploitability, compromise, or business intent when those cannot be proven remotely.

Associated attack or threat scenario

Threat type SPF policy invalidation

How the attack or failure scenario works

An invalid SPF policy is evaluated as a permanent error rather than as the intended allow or deny decision. This may cause legitimate mail rejection and can remove an authentication control that would otherwise help receivers identify forged envelope senders.

Conditions and limitations

  • A malformed SPF record is published in authoritative DNS.
  • Receivers evaluate the affected domain for SPF.
  • Security impact depends on receiver policy, DMARC alignment, and whether DKIM supplies an independent aligned pass.

Why it matters

Security and business impact Invalid SPF mechanisms, modifiers, qualifiers, or ordering can produce a permanent error and make the policy unusable.

Step-by-step fix

Where to make the change

  • The authoritative DNS zone for the registrable domain.
  • The outbound or inbound mail platform when sender authorization, signing, or routing is involved.
  • The DMARC reporting mailbox or reporting service when aggregate reports are required.

Remediation procedure

  1. Use the scanner evidence to identify the exact invalid token or duplicate modifier.
  2. Correct mechanisms, CIDR lengths, qualifiers, and required values according to RFC 7208.
  3. Keep one `redirect=` and one `exp=` modifier at most, and place all policy content in one logical TXT record.
  4. Test the new record with representative legitimate and unauthorized senders before raising enforcement.

Commands and configuration examples

Replace example values with the hostname, selector, IP address, port, provider, or policy values shown in your SecuTest evidence. Review every example before production use.

Valid syntax example
example.com. 3600 IN TXT "v=spf1 ip4:192.0.2.0/24 include:spf.protection.outlook.com -all"

Inspect TXT strings
dig +short TXT example.com

Verify the fix

  1. Run `dig +short TXT example.com` and inspect the complete reconstructed value.
  2. Validate every include and redirect target externally.
  3. Send a test message and confirm the receiver reports `spf=pass`, not `permerror`.
  4. Repeat SecuTest and verify that both syntax and recursive checks complete.
Confirm the externally visible result

After DNS, CDN, certificate, mail, or application propagation completes, run a fresh SecuTest scan and compare the new evidence with the original finding.

Re-scan your domain

Common mistakes

  • Publishing commas between mechanisms instead of spaces.
  • Using `include=` instead of `include:`.
  • Adding quotes inside the TXT value rather than letting the DNS control panel handle quoting.

Authoritative references