Email address check

Returns JSON with an email address check: syntax, domain and MX records, disposable, free and role account flags, SPF and DMARC, and a verdict on whether the domain can receive mail.

Use when you need email validation or to verify email addresses (domain, MX records) before sending, signup or lead scoring.

Do not use when you need to confirm the mailbox itself exists (no SMTP probe is done) or to send email.

Price: 0.005 USDC per call (x402, eip155:8453). Typical response time: 800 ms (p95).

Call it over HTTP (x402)

POST https://x402-gateway.blackwoodstate8.workers.dev/v1/email-check. A request without payment gets 402 Payment Required with the PAYMENT-REQUIRED header; any x402 client signs an EIP-3009 authorization and retries with PAYMENT-SIGNATURE (or X-PAYMENT). Invalid input is answered with 400 and not charged.

curl -i -X POST https://x402-gateway.blackwoodstate8.workers.dev/v1/email-check -H 'content-type: application/json' -d '{"email":"postmaster@ietf.org"}'

Call it over MCP

Streamable HTTP at https://x402-gateway.blackwoodstate8.workers.dev/mcp, tool email-check_v1. Payment goes in _meta["x402/payment"]; without it the tool returns the payment requirements.

Input

Example:

{
  "email": "postmaster@ietf.org"
}

Output

Real example:

{
  "email": "postmaster@ietf.org",
  "normalized": "postmaster@ietf.org",
  "syntaxValid": true,
  "domain": "ietf.org",
  "disposable": false,
  "freeProvider": false,
  "roleAccount": true,
  "domainExists": true,
  "mx": [
    {
      "priority": 0,
      "host": "mx.ietf.org"
    }
  ],
  "acceptsMail": true,
  "spf": "v=spf1 ip4:166.84.6.31 ip4:166.84.7.238 ip6:2602:f977:800:f7f6::/64 ip4:166.84.7.34 ip6:2602:f977:800::e276:63ff:fe66:3400 include:_spf.google.com include:spf.hostedrt.com ~all",
  "dmarc": "v=DMARC1; p=none; rua=mailto:dmarc_agg@vali.email,mailto:dmarc-report@ietf.org",
  "dmarcPolicy": "none",
  "verdict": "deliverable_domain",
  "reasons": [
    "role_account"
  ],
  "smtpChecked": false
}

{
  "type": "object",
  "properties": {
    "email": {
      "type": "string"
    },
    "normalized": {
      "type": [
        "string",
        "null"
      ]
    },
    "syntaxValid": {
      "type": "boolean"
    },
    "domain": {
      "type": [
        "string",
        "null"
      ]
    },
    "disposable": {
      "type": "boolean"
    },
    "freeProvider": {
      "type": "boolean"
    },
    "roleAccount": {
      "type": "boolean"
    },
    "domainExists": {
      "type": [
        "boolean",
        "null"
      ]
    },
    "mx": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "priority": {
            "type": "number"
          },
          "host": {
            "type": "string"
          }
        },
        "required": [
          "priority",
          "host"
        ],
        "additionalProperties": false
      }
    },
    "acceptsMail": {
      "type": "boolean"
    },
    "spf": {
      "type": [
        "string",
        "null"
      ]
    },
    "dmarc": {
      "type": [
        "string",
        "null"
      ]
    },
    "dmarcPolicy": {
      "type": [
        "string",
        "null"
      ]
    },
    "verdict": {
      "type": "string",
      "enum": [
        "deliverable_domain",
        "risky",
        "undeliverable",
        "invalid"
      ]
    },
    "reasons": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "smtpChecked": {
      "type": "boolean"
    }
  },
  "required": [
    "email",
    "normalized",
    "syntaxValid",
    "domain",
    "disposable",
    "freeProvider",
    "roleAccount",
    "domainExists",
    "mx",
    "acceptsMail",
    "spf",
    "dmarc",
    "dmarcPolicy",
    "verdict",
    "reasons",
    "smtpChecked"
  ],
  "additionalProperties": false
}

More

Free schema and example: GET https://x402-gateway.blackwoodstate8.workers.dev/v1/email-check. OpenAPI 3.1 · llms.txt · All services