Email Deliverability Check

Check an email address for deliverability: syntax, canonical form, MX, SPF, DMARC, disposable domain. One verdict with reasons and sources. DNS-over-HTTPS only, no mailbox probing. Not charged if the DNS lookup fails.

Price: $0.0032 per call, USDC on Base (x402). Also available as the MCP tool email_check at https://grokzilla.shop/mcp.

Public DNS only, over DNS-over-HTTPS (Cloudflare, Google as fallback): MX (null MX per RFC 7505, implicit MX via A), SPF, DMARC, plus a disposable-domain flag from the CC0 disposable-email-domains list. No SMTP connection and no mailbox probing, so mailbox_checked is always false: a deliverable domain can still reject one mailbox.

Verdicts: deliverable (MX ok), risky (implicit MX, unresolvable MX host, or disposable domain), undeliverable (NXDOMAIN, null MX, or nowhere to deliver).

Call

POST /api/skills/email-check

{"email": "[email protected]"}

email (required): string
request_id (optional): Optional idempotency key. Echoed back; a credit-pack redemption with the same request_id and body is charged once.

Not charged

Every non-200 has charged: false and is never settled.

422 invalid_params / 400 invalid_params: body fails the schema (checked before the 402).
400 before payment: not an address, IP-literal or private/reserved domains (.local, .internal, .test …).
503 dns_unavailable: no DoH resolver answered.

Response (paid 200)

Same envelope on every data service: ok, service, version, summary, data, confidence, sources, generated_at, data_as_of, charged, warnings, next.

{
  "ok": true,
  "skill": "email_check",
  "service": "email_check",
  "version": "1.0.0",
  "summary": "deliverable: MX ok (gmail-smtp-in.l.google.com), SPF ok, DMARC p=none",
  "data": {
    "email": "[email protected]",
    "local": "jane.doe+news",
    "domain": "gmail.com",
    "verdict": "deliverable",
    "reasons": [
      "MX ok (gmail-smtp-in.l.google.com)",
      "SPF ok",
      "DMARC p=none"
    ],
    "syntax_valid": true,
    "canonical": "[email protected]",
    "canonical_rule": "gmail: dots and +tag removed",
    "plus_tag": "news",
    "domain_exists": true,
    "mx": [
      {
        "priority": 5,
        "host": "gmail-smtp-in.l.google.com"
      },
      {
        "priority": 10,
        "host": "alt1.gmail-smtp-in.l.google.com"
      },
      {
        "priority": 20,
        "host": "alt2.gmail-smtp-in.l.google.com"
      },
      {
        "priority": 30,
        "host": "alt3.gmail-smtp-in.l.google.com"
      },
      {
        "priority": 40,
        "host": "alt4.gmail-smtp-in.l.google.com"
      }
    ],
    "null_mx": false,
    "implicit_mx": false,
    "mx_host_resolves": true,
    "spf": {
      "present": true,
      "record": "v=spf1 redirect=_spf.google.com",
      "count": 1
    },
    "dmarc": {
      "present": true,
      "record": "v=DMARC1; p=none; sp=quarantine; rua=mailto:[email protected]",
      "p": "none",
      "sp": "quarantine",
      "pct": null,
      "rua": true
    },
    "disposable": false,
    "role_account": false,
    "free_provider": true,
    "mailbox_checked": false
  },
  "confidence": 0.85,
  "sources": [
    {
      "name": "Cloudflare DoH",
      "url": "https://cloudflare-dns.com/dns-query?name=gmail.com",
      "fetched_at": "2026-10-17T11:12:49Z"
    },
    {
      "name": "disposable-email-domains",
      "url": "https://github.com/disposable-email-domains/disposable-email-domains (CC0-1.0)",
      "fetched_at": "2026-10-17T11:12:49Z",
      "list_date": "2026-10-16"
    }
  ],
  "generated_at": "2026-10-17T11:12:49Z",
  "data_as_of": "2026-10-17T11:12:49Z",
  "charged": true,
  "warnings": [
    "mailbox existence is not checked (no SMTP probing); a deliverable domain can still reject this mailbox"
  ],
  "next": [
    "phone_normalize",
    "ip_intel"
  ]
}