Lookproof Browse tools

Mail provider detection API

Matches the MX hosts and the domains in the SPF include tree against a fixed, versioned list of about 30 providers. Each match says whether it came from MX, SPF or both; the provider behind the MX host with the lowest preference is the primary one.

GET https://api.lookproof.dev/v1/mail/provider

Updated 2026-10-09

Examples use the Base (eip155:8453) network.

Input

Query parameters.

NameTypeRequiredLimitsDescription
domainstringYes1–1024 charactersThe domain to check, for example example.com.

Example request

curl -i 'https://api.lookproof.dev/v1/mail/provider?domain=example.com'
import asyncio
import os

from eth_account import Account
from x402 import x402Client
from x402.http.clients import x402HttpxClient
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact import register_exact_evm_client


async def main() -> None:
    signer = EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"]))
    client = register_exact_evm_client(x402Client(), signer, networks="eip155:8453")
    async with x402HttpxClient(client) as http:
        response = await http.get('https://api.lookproof.dev/v1/mail/provider', params={'domain': 'example.com'})
        response.raise_for_status()
        print(response.json())


asyncio.run(main())

import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY);
const fetchWithPayment = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(account) }],
});

const response = await fetchWithPayment("https://api.lookproof.dev/v1/mail/provider?domain=example.com");
console.log(await response.json());

curl: unpaid request — returns 402 with the price (PAYMENT-REQUIRED). The Python and JavaScript clients pay it and send the request again. Only ordinary wallets (EOA) can pay; smart-contract wallets get a 402 without charge. See payments.

Example response

{
  "checked_at": "2026-10-24T12:00:00Z",
  "data": {
    "domain": "example.com",
    "list_version": "2026-10-26",
    "primary": null,
    "providers": []
  },
  "endpoint": "mail.provider",
  "findings": [
    {
      "code": "MAIL_PROVIDER_UNKNOWN",
      "evidence": {
        "count": 1,
        "items": [
          {
            "domain": "example.com"
          }
        ]
      },
      "explanation": "The domain receives mail, but none of its MX host names matches a provider on Lookproof's fixed list. The domain may run its own mail servers or use a provider that is not on the list.",
      "message": "The MX hosts match no provider on the list.",
      "recommendation": null,
      "severity": "info"
    }
  ],
  "meta": {
    "cache_hit": false,
    "duration_ms": 42,
    "fresh_until": "2026-10-24T12:05:00Z",
    "observed_at": "2026-10-24T12:00:00Z",
    "resolver": "example",
    "source": "dns"
  },
  "request_id": "req_aaaaaaaaaaaaaaaaaaaaaaaaaa",
  "schema_version": "1.0",
  "status": "info"
}

Response fields

FieldMeaning
request_idUnique id of this request. Quote it when you contact support.
endpointThe endpoint id, for example mail.spf.
schema_versionVersion of the response format, currently 1.0.
checked_atWhen the check ran (ISO 8601, UTC).
statusok, info, warning or error from the worst finding, or unknown when the check was incomplete. unknown is not an error in the domain.
dataThe check's own data. Its fields are listed below.
findingsWhat was found: code, severity, message, explanation and evidence.
metaDuration, cache use, resolver and how long the result stays fresh.

Fields in data

FieldType
domainstring
providersarray of ProviderMatch
primarystring or null
list_versionstring

Status codes

StatusCodeMeaningDo you pay?
200—The result is delivered, also when it has negative findings.Yes: charged once per payment; redelivery of the same payment is free
402—Payment is required, or the attached payment was refused. The body states the price.No
400bad_requestThe request is malformed.No
409payment_in_progress, payment_bound_to_other_requestThis payment is already being processed, or it is bound to a different request. No new payment is taken.No
422invalid_inputThe input failed validation on a request that carries a payment; nothing is charged. Without a payment, invalid input gets a 402 whose error field names the problem.No
429rate_limitedToo many requests from this IP address or payer.No
502check_failedThe check could not be completed.No
503busy, unavailable, payments_unavailableThe service is busy or temporarily unavailable.No
504deadline_exceededThe check ran out of time.No

Errors use the common error body. See errors.

Findings this endpoint can return

Mail provider (3)
  • Info MAIL_NO_MX The domain has no MX records, so no inbound mail provider can be named.
  • Info MAIL_PROVIDER_MIXED SPF authorises a mailbox provider that does not receive the domain's mail.
  • Info MAIL_PROVIDER_UNKNOWN The MX hosts match no provider on the list.
Check (1)
DNS (3)