SPF Lookup Counter Form
Use a live domain, paste a manual SPF record, or do both. The calculator supports nested includes, redirects, MX expansion, and export features.
Example Data Table
| Domain | SPF Snippet | Lookup Terms | Estimated DNS Queries | Status |
|---|---|---|---|---|
| example.com | v=spf1 include:_spf.google.com include:mail.zendesk.com -all | 6 | 8 | Monitor Closely |
| sample.net | v=spf1 a mx include:_spf.mailhost.net -all | 4 | 7 | Healthy |
| acme.org | v=spf1 include:a.example.net include:b.example.net redirect=_spf.acme.net | 7 | 9 | Near Limit |
These are illustrative examples to show how the output table may look.
Formula Used
Lookup Terms Used = Include + A + MX + PTR + Exists + Redirect + nested lookup-causing terms discovered in included or redirected SPF records.
Estimated DNS Queries = Lookup Terms Used + expanded MX host address lookups when MX expansion is enabled.
Remaining Headroom = Selected Lookup Limit - Lookup Terms Used.
Risk Logic = Healthy when comfortably below limit, moderate near seven or more terms, high near the ceiling, and critical above the selected limit.
Important Note: This calculator is designed for planning and auditing. Real receiver behavior can vary with macros, cached DNS responses, provider changes, and resolver limits.
How to Use This Calculator
- Enter the domain if you want live SPF fetching from DNS.
- Paste a manual SPF record when testing edits before deployment.
- Set the lookup limit and recursion depth for your audit model.
- Enable nested resolution to count includes and redirects recursively.
- Enable MX expansion if you want broader operational query estimation.
- Press the calculate button to show results above the form.
- Review the chart, summary cards, warnings, and detailed mechanism table.
- Use the CSV or PDF buttons to save the current report.
Frequently Asked Questions
1. What does this calculator count?
It counts SPF terms that trigger DNS lookups, including nested include and redirect chains. It also estimates operational DNS queries by expanding MX host address checks when that option is enabled.
2. Why is the value ten so important?
SPF evaluation should stay within ten lookup-causing terms. Crossing that boundary can produce permerror results, inconsistent delivery, or authentication failures on strict receiving systems.
3. Does every MX mechanism equal one query?
Not always. The MX term triggers an MX lookup first, then address lookups for returned mail hosts. This page estimates both so you can view policy budget and likely DNS workload together.
4. Are include and redirect the same thing?
No. Include asks another policy to authorize a sender. Redirect hands evaluation to another record when no earlier mechanism matched. Both still consume lookup budget and may deepen recursion.
5. Should I flatten my SPF record?
Flattening can reduce nested lookups, but it increases maintenance and may become stale when providers change infrastructure. Use it carefully, monitor provider updates, and keep the record understandable.
6. Can I test a record before publishing it?
Yes. Manual mode is ideal for safe pre-deployment checks. Supplying the domain alongside the pasted record improves accuracy for relative a or mx mechanisms.
7. What does negative headroom mean?
It means the evaluated policy used more lookup-causing terms than your selected limit. That is a strong signal the record should be simplified before production use.
8. Why are warnings shown in the result?
Warnings highlight loops, missing nested records, unavailable DNS results, or estimation assumptions. They help explain why a policy may still be risky even when the headline count looks acceptable.