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Lookproof MTA-STS Checker
x402
Lookproof MTA-STS Checker is a paid API for AI agents from api.lookproof.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-31).
Checks a domain's full MTA-STS setup (RFC 8461) including DNS record, HTTPS policy file, certificate validity, MX coverage, mode, max_age, and TLS-RPT record (RFC 8460)
Price / call$0.02
Success—
StatusUnknown
How this service works
Check SPF, DMARC, DKIM, MTA-STS, DNSSEC and more, with results that explain what was found and why. Free browser checks and a pay-per-request API with x402.
Output
Returns a structured report covering: presence and validity of the _mta-sts TXT DNS record, reachability of the HTTPS policy file (with certificate chain check and redirect detection), parsed policy fields (mode: none/testing/enforce, max_age), whether every MX host for the domain is listed in the policy, and status of the TLS-RPT record at _smtp._tls. Failures include per-check error messages explaining exactly what is misconfigured.
Example use cases
Debug sender MTA-STS failures
“Senders are reporting MTA-STS failures for payments.stripe.com — can you check the MTA-STS configuration and tell me exactly what's broken, whether it's the DNS record, the policy file, the certificate, or MX coverage?”
Pre-deployment email security audit
“Before we go live, check if mailchimp.com has MTA-STS properly set up in enforce mode with a valid HTTPS policy file and all MX servers covered, and whether TLS-RPT is also in place.”
Verify inbound TLS downgrade protection
“Does fastmail.com protect inbound mail against TLS downgrade attacks? Check its MTA-STS policy — I want to know the mode, max_age, whether the certificate is trusted, and if every MX host is listed in the policy.”
Technical details
Endpoint
GEThttps://api.lookproof.dev/v1/mail/mta-sts?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need a complete, authoritative MTA-STS compliance check for a single domain — covering DNS record, HTTPS policy file integrity, certificate validity, MX host coverage, and TLS-RPT in one call. Prefer this over a generic full-domain mail security report when you specifically need to diagnose MTA-STS issues or confirm RFC 8461 compliance without the overhead of a broader SPF/DKIM/DMARC audit.
Side effects
- Domain does not exist or has no DNS records — returns not-found or DNS error
- _mta-sts DNS record missing or malformed — reported as record absence or parse failure
- Policy file at https://mta-sts.{domain}/.well-known/mta-sts.txt unreachable — HTTP error or timeout reported
- Policy file served over redirect — flagged as non-compliant per RFC 8461
- TLS certificate for mta-sts subdomain invalid or untrusted — cert check failure reported
- MX hosts not fully covered by policy — lists uncovered hostnames
- TLS-RPT record absent or malformed — reported separately in the TLS-RPT section
- Invalid domain input (too long, bad format) — validation error returned
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Tags
x402
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