Email validation API for agents, screening only.

Screen one email address for $0.003 per call ($3 per 1,000). Pay through x402 in USDC on Base or Solana. No account, no API key: your client pays the 402 and gets the answer. Checks syntax, mail-domain DNS, disposable domains and common typos; it does not verify that the mailbox exists or that mail will be delivered. Built for the moment an address arrives from a form, a scrape or a CRM and you must decide whether it is worth sending to.

Screening only: syntax, DNS mail exchanger, disposable-domain list, role-account and typo heuristics. It does not verify that the mailbox exists or that mail will be delivered.

Run your first email check See a sample response

What one check does

• Syntax: the address is well formed (RFC-style local part and domain).
• DNS mail exchanger: the domain publishes MX records, falls back to an A record, declares null MX, has no mail host, or does not exist.
• Disposable domain: the domain is on a public list of throwaway providers.
• Heuristics: role account (info@, sales@ …), free provider, and a typo suggestion (gmial.com → gmail.com).

The verdict is one of domain_accepts_mail, risky, disposable, undeliverable or unknown, with every reason listed. A working mail exchanger means the domain accepts mail; it never means the mailbox exists. Role and free-provider flags are signals for your own routing rules, not rejections.

GET /v1/email/verify $0.003 per call

Use when an agent needs email validation, screening only, for an address from a form, a scrape or a CRM and must decide whether it is worth sending to. Screens the address: syntax, DNS mail exchanger, disposable domain, role account, free provider and common typos. It does not verify that the mailbox exists. A DNS failure answers 503 and is not charged.

curl -i "https://api.paywallwatch.com/v1/email/verify?email=jane%40iana.org"   # unpaid: answers 402 with the payment terms

{
  "email": "jane@iana.org",
  "valid_syntax": true,
  "dns_status": "ok",
  "has_mx": true,
  "disposable": false,
  "role_account": false,
  "free_provider": false,
  "suggestion": null,
  "verdict": "domain_accepts_mail",
  "reasons": [],
  "mailbox_verified": false,
  "screening_note": "Screening only: syntax, DNS mail exchanger, disposable-domain list, role-account and typo heuristics. It does not verify that the mailbox exists or that mail will be delivered.",
  "checked_at": "2026-10-20T09:12:00Z"
}

An excerpt, not a script to copy: it omits the charge cap and the check of the signing terms. The complete script, capped at $0.003 per run, is on the quickstart.

// Excerpt. Expected price $0.003. Use the capped quickstart for the complete runnable example.
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm/exact/client";

const client = new x402Client();
client.register("eip155:*", new ExactEvmScheme(account)); // a viem account holding USDC on Base
const paid = wrapFetchWithPayment(fetch, client);
const res = await paid("https://api.paywallwatch.com/v1/email/verify?email=jane%40iana.org"); // pays the 402 once, returns the JSON above

When you are charged

The result is computed before settlement. A confirmed settlement failure returns a 402 instead of the result. If a response is lost or settlement times out, check the transaction before retrying: a new authorization can charge again.

Developer testing

Prove that your client pays a 402 and retries before you spend on real checks.

GET /v1/ping $0.01 per call

Use when testing an x402 client end to end. Returns ok and the server time; costs one cent.

curl -i "https://api.paywallwatch.com/v1/ping"   # unpaid: answers 402 with the payment terms

{
  "ok": true,
  "at": "2026-10-20T09:12:00Z"
}

For agents and tools

• OpenAPI 3.1 document: both routes, the query parameters, the explicit response schemas (every field, every verdict, mailbox_verified always false) and the payment metadata (x-payment-info, x402).
• Service descriptor: name, prices, networks, how to pay, and each route with its input schema, output schema and example. A plain REST API paid per call, not an A2A agent.
• llms.txt: the same in Markdown for language-model crawlers.

Data handling and support

• The address is parsed inside the service. Its domain, never the local part, is sent to Cloudflare's DNS-over-HTTPS resolver (cloudflare-dns.com) for the MX and A lookups. Payment authorizations are sent to the facilitator for verification and settlement.
• Our measurement records the route, the outcome class, the settlement network, whether the payer was one of our own wallets, and the latency; for a visit to these pages it also records a coarse class of where a visit came from (another page of this site, a catalog, a search engine, or none), never the referring URL. It never records the address or a payment payload.
• The address travels in the request URL, and Cloudflare's invocation log for the service records each request: its method and URL, its request headers including the payment header, the caller's IP address and the location Cloudflare derives from it, and the response status. On our current plan that log is kept for three days. We keep no other copy and have no account to tie it to.
• Your paying wallet address is on the public chain, as with every x402 payment.

Questions, integration help or a problem with a charge: support@auraaia.com. Replies are checked manually; no response time is promised.