# Agent Email Check (Single Address)

> Agent Email Check (Single Address) is a paid API for AI agents from mail.halowerk.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-13).

Verifies a single email address using DNS and blocklist checks, with an optional SMTP probe, returning a conservative verdict that distinguishes unknown-but-routable from confirmed-valid.

## Facts

- Endpoint: POST https://mail.halowerk.com/email
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-email-check-single-address-8bd14886
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Uj2BT9uIJur06ecs7ke6u

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability agent-email-check-single-address-8bd14886 -d '<json body>'
```

Example prompt: Can you verify whether john.doe@example.com is a real, deliverable email address — go ahead and run the SMTP probe too so we get a definitive answer rather than just 'unknown'.

## When to prefer this

Choose this endpoint when you need a conservative, non-spammy email check that distinguishes between 'definitely invalid', 'probably routable but unconfirmed', and 'confirmed valid via SMTP'. It is especially useful when false positives (treating bad emails as good) are costly — e.g. CRM hygiene, outreach campaigns, or signup validation — and when you want honest uncertainty rather than an optimistic guess. Prefer the optional SMTP probe when a definitive answer is needed and the target domain is not known to block probes.

## Known failure modes

- Email address is malformed — returns invalid immediately without DNS lookup
- Domain is routable but smtp_check was false — verdict is 'unknown', not 'valid'
- SMTP probe is rate-limited or throttled — only one attempt per target, never retried, may return inconclusive
- Target mail server blocks or graylists SMTP probes — probe result may be unreliable
- Domain does not exist or has no MX records — returns unroutable/invalid

## How this service works

DNS and list based verification. Never claims that a mailbox exists without evidence: without an SMTP probe the verdict for a routable address is "unknown", not "valid".

## Output

A JSON verdict indicating whether the email address is valid, invalid, or unknown (routable domain but mailbox unconfirmed without SMTP probe). Includes DNS resolution status, domain routability, any blocklist signals, and — if smtp_check was requested — the result of a one-time SMTP connection attempt to confirm mailbox existence.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "email": {
   "type": "string",
   "description": "The email address to check."
  },
  "smtp_check": {
   "type": "boolean",
   "default": false,
   "description": "Ask for an optional SMTP probe. Off by default, heavily throttled, one attempt per target and never retried. Without it the verdict of a routable address stays \"unknown\"."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-email-check-single-address-8bd14886/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mail.halowerk.com](https://www.zero.xyz/host/mail.halowerk.com/llms.txt)