# Agent Email Check

> Address in, verdict and confidence out. Pay per call in USDC over x402. No signup, no API key, no dashboard.

## What this is

A machine facing API for agents that qualify leads or clean address lists. Per address it reports syntax,
whether the domain accepts mail at all, the MX hosts and the mail provider behind them, whether the domain is a
disposable provider, whether the local part is a role account, a typo suggestion for lookalike domains, a
catch-all estimate, and a verdict with a confidence between 0 and 1. Payment happens inside the request: call
the endpoint, receive HTTP 402 with the accepted terms, retry with a signed payment header.

## Endpoints

- POST https://mailcheck.netzhandwerker.de/email — 0.001 USDC — one address.
- POST https://mailcheck.netzhandwerker.de/email/batch — 0.0006 USDC per address, up to 100 per call — the 402 quotes the exact amount.

## What the verdicts mean

- deliverable: The mail server accepted this recipient and the domain is not catch-all. Only reachable with an SMTP probe.
- undeliverable: The mail server rejected this recipient permanently.
- invalid: The address cannot receive mail: broken syntax, no MX and no A record, or a null MX record.
- risky: A mail route exists, but a concrete negative signal is attached: disposable provider, catch-all domain or a likely typo.
- unknown: A mail route exists and nothing is known about this specific mailbox. This is the honest default without an SMTP probe.

## The rule this service is built on

- This service never claims that a mailbox exists without evidence.
- DNS proves that a domain accepts mail. It proves nothing about the mailbox in front of the at sign.
- Without an SMTP probe the verdict of a routable address is "unknown" and the confidence is capped at 0.7.
- The SMTP probe is optional, off by default, heavily throttled, and contacts a target once without any retry.
- A temporary 4xx reply is treated as no answer, not as a yes.

If you need a hard yes on a mailbox, no DNS based service can give it to you, and this one will not pretend
otherwise. What it does give you is a cheap, fast and truthful filter that removes the addresses which cannot
work before you spend a send on them.

## Discovery without payment

- https://mailcheck.netzhandwerker.de/openapi.json
- https://mailcheck.netzhandwerker.de/.well-known/x402
- https://mailcheck.netzhandwerker.de/mcp (Model Context Protocol, tools/list needs no payment)
- https://mailcheck.netzhandwerker.de/pricing
- https://mailcheck.netzhandwerker.de/health

## Operating rules

- MX and catch-all are cached per domain for 24 hours. Syntax, role and disposable are recomputed every call.
- The disposable and role lists are refreshed daily.
- An unpaid request receives the 402 with the price, never an error message.
- A malformed body is rejected before settlement and never charged.

## Operator

Die Netzhandwerker, IT-Manufaktur für Digitales und Sensorik. https://netzhandwerker.de