Email auth check

Email authentication check for a domain. Returns the SPF record with its DNS lookup count and all qualifier, the DMARC policy and report addresses, MX hosts, MTA-STS and BIMI records, DKIM keys found on common selectors, a grade from A to F and a list of issues. Use to diagnose deliverability or spoofing risk. DKIM is checked on common selectors only. Typical response under 1 s. Failed calls are not charged.

Try one call free

5 free calls a day per address, no payment. Demo inputs travel in the web address, which logs can record, so use the paid route for anything private.

The result appears here.

Example

Request body for POST /v1/email-auth-check:

{
  "domain": "example.org"
}

Response:

{
  "domain": "example.org",
  "spf": {
    "record": "v=spf1 include:_spf.google.com ~all",
    "lookups": 4,
    "all_qualifier": "~all",
    "valid": true,
    "error": null
  },
  "dmarc": {
    "record": "v=DMARC1; p=quarantine; rua=mailto:[email protected]",
    "policy": "quarantine",
    "subdomain_policy": null,
    "pct": 100,
    "rua": [
      "mailto:[email protected]"
    ]
  },
  "mx": [
    {
      "preference": 1,
      "host": "smtp.google.com."
    }
  ],
  "mta_sts": {
    "record": null
  },
  "bimi": {
    "record": null
  },
  "dkim": {
    "checked_selectors": [
      "google",
      "selector1",
      "selector2",
      "default",
      "k1",
      "s1",
      "s2",
      "mail",
      "dkim",
      "smtp"
    ],
    "found": [
      "google"
    ]
  },
  "grade": "A",
  "issues": [],
  "checked_at": "2026-10-22T09:00:00+00:00"
}

Call it with x402

Any x402 client works: call, read the price in the 402, pay, call again. With curl you see the terms:

curl -i -X POST https://quantagentshop.com/v1/email-auth-check \
  -H 'content-type: application/json' \
  -d '{"domain": "example.org"}'

HTTP/1.1 402 Payment Required
PAYMENT-REQUIRED: (the terms below, base64)

{"x402Version": 2, "error": "payment_required", "accepts": [{"scheme": "exact", "network": "eip155:8453", "amount": "1300", "payTo": "0x4d8d8D4f04512029172e0176744Eec4AE5238309", ...}], ...}

# amount is in millionths of a USDC. Pay one of accepts, then send the same request again with the PAYMENT-SIGNATURE header.

In JavaScript, @x402/fetch pays and retries for you:

// npm install @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY); // a wallet holding a little USDC
const client = new x402Client().register("eip155:*", new ExactEvmScheme(signer));
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

const res = await fetchWithPayment("https://quantagentshop.com/v1/email-auth-check", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({"domain": "example.org"}),
});
console.log(await res.json());

Use it over MCP

Add the remote MCP server, then call quantagentshop_email_auth_check. The free quantagentshop_quote tool gives the price and pay-to address and checks your arguments before you pay.

{
  "mcpServers": {
    "quantagentshop": {
      "url": "https://quantagentshop.com/mcp"
    }
  }
}

Terms, privacy and sources are on the policies page; live figures on the status page.