# dns-a-smtp-subdomain

> dns-a-smtp-subdomain is a paid API for AI agents from dns.intel.rallylive.ca, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-21).

Looks up the A record for smtp.<domain> via Cloudflare DNS-over-HTTPS and reports whether the SMTP host exists, its IP records, and TTL.

## Facts

- Endpoint: GET https://dns.intel.rallylive.ca/dns/host/smtp/a?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/dns-a-smtp-subdomain-12217362
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_GvSSqjR7Wc5RZ0NiKrp8a

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 dns-a-smtp-subdomain-12217362
```

Example prompt: Can you check whether smtp.acmecorp.com exists as a DNS host — I need to know if there's an A record for it and what IP it resolves to?

## When to prefer this

Choose this endpoint when you need a fast, cheap ($0.01) existence check specifically for the smtp.<domain> subdomain via Cloudflare's reliable DoH resolver, without needing to enumerate or scan subdomains broadly. Ideal for email infrastructure validation, onboarding checks, or pre-flight configuration verification where only the A record of the smtp host matters.

## Known failure modes

- Domain does not exist — NXDOMAIN response with no records
- smtp subdomain not configured — NOERROR but empty answer section
- Invalid or malformed domain input — API may return error or unexpected result
- Cloudflare DoH upstream timeout or outage — service may return error
- Network latency spike causing slow response

## How this service works

A record of smtp.<domain>: looks up the smtp host under the domain you give (A via Cloudflare DoH) and reports whether it exists, its records and TTL. Quick existence check for common hosts like smtp without enumerating subdomains. $0.01 per lookup.

## Output

Returns whether the A record for smtp.<domain> exists, along with the resolved IP address(es), the TTL value, and the DNS response code — giving a quick picture of whether the SMTP subdomain is live and reachable.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/dns-a-smtp-subdomain-12217362/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from dns.intel.rallylive.ca](https://www.zero.xyz/host/dns.intel.rallylive.ca/llms.txt)