# Lookproof MTA-STS Checker

> 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)

## Facts

- Endpoint: GET https://api.lookproof.dev/v1/mail/mta-sts?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/lookproof-mta-sts-checker-a66f4c17
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6R89KO7gjF7-XJWBw5kts

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability lookproof-mta-sts-checker-a66f4c17
```

Example prompt: Check whether acmecorp.com has a valid MTA-STS setup — I want to know if the DNS record is correct, the policy file is reachable over HTTPS without redirects, all MX hosts are covered, and whether TLS-RPT is configured too.

## When to prefer this

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.

## Known failure modes

- 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

## 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.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "title": "DomainInput",
     "required": [
      "domain"
     ],
     "properties": {
      "domain": {
       "type": "string",
       "title": "Domain",
       "examples": [
        "example.com"
       ],
       "maxLength": 1024,
       "minLength": 1
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/lookproof-mta-sts-checker-a66f4c17/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.lookproof.dev](https://www.zero.xyz/host/api.lookproof.dev/llms.txt)