Email deliverability check

End-to-end email-auth report for a domain: SPF + DMARC + DKIM (probes common selectors automatically) + MX records + score 0–100. Send POST /api/email-deliverability with the required field domain and pay $0.002 per call over x402 or MPP (there is no free tier). It returns a JSON object with domain, score, summary, spf, dmarc and 4 more.

The one call to make when 'why is our mail going to spam?' lands in your inbox.

Category: Network & domains · Tags: email email-auth deliverability spf dmarc dkim mx audit

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/email-deliverability \
  -H "Content-Type: application/json" \
  -d '{"domain":"google.com"}'

Without payment this returns HTTP 402 Payment Required with the exact price for email-deliverability; any x402 v2 or MPP client pays it and retries.

Example response

{
  "domain": "google.com",
  "score": 90,
  "summary": "good",
  "spf": {
    "hasRecord": true,
    "all": "softfail",
    "valid": true,
    "lookupCount": 1
  },
  "dmarc": {
    "hasRecord": true,
    "policy": "reject",
    "percent": 100,
    "valid": true
  },
  "dkim": {
    "found": [
      {
        "selector": "20221208",
        "bits": 2048,
        "valid": true
      }
    ],
    "probed": [
      "google",
      "selector1",
      "default",
      "20221208"
    ]
  },
  "mx": {
    "count": 5,
    "records": [
      "smtp.google.com"
    ]
  },
  "checks": [
    {
      "check": "spf",
      "status": "pass",
      "detail": "SPF record present, 1 DNS lookup, ~all qualifier"
    },
    {
      "check": "dmarc",
      "status": "pass",
      "detail": "p=reject at 100% - strict enforcement"
    },
    {
      "check": "dkim",
      "status": "pass",
      "detail": "Found DKIM at selector 20221208 (2048-bit RSA)"
    },
    {
      "check": "mx",
      "status": "pass",
      "detail": "5 MX records configured"
    }
  ],
  "queriedAt": "2026-06-19T20:00:00.000Z"
}

From an MCP client

catalog.call {
  "slug": "email-deliverability",
  "params": {
    "domain": "google.com"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for email-deliverability; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• domain is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A GET or HEAD to /api/email-deliverability returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/email-deliverability", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "domain": "google.com"
  }),
});

Part of these workflows

Email deliverability check is one step in these 2 skill packs, each sold as a single call:

• Email deliverability - Diagnose why a domain's email lands in spam: SPF posture, DMARC policy, DKIM key strength, MX targets, and a composite 0–100 score.
• Email security - Full email auth posture: SPF, DMARC, DKIM, and composite deliverability score in one call.

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