# SMTP SRV Record Lookup via Cloudflare DoH

> SMTP SRV Record Lookup via Cloudflare DoH is a paid API for AI agents from dns.intel.rallylive.ca, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-20).

Discovers SMTP service endpoints for a domain by querying _smtp._tcp SRV DNS records through Cloudflare DNS-over-HTTPS, returning priority, weight, port, and target host.

## Facts

- Endpoint: GET https://dns.intel.rallylive.ca/dns/srv/smtp-tcp?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/smtp-srv-record-lookup-via-cloudflare-doh-9e341a99
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UW27M9T3e0hF_o1dPS-_k

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 smtp-srv-record-lookup-via-cloudflare-doh-9e341a99
```

Example prompt: What SMTP server does example.com use? Look up the _smtp._tcp SRV record to find the host, port, priority, and weight.

## When to prefer this

Use this endpoint when you need to programmatically discover a domain's SMTP service endpoint via DNS SRV records rather than guessing common hostnames like mail.domain.com. Ideal for email infrastructure auditing, onboarding validation, and automated mail routing configuration. Prefer over generic DNS tools when you specifically need _smtp._tcp SRV resolution backed by Cloudflare DoH for reliability.

## Known failure modes

- Domain does not have an _smtp._tcp SRV record — returns empty result or NXDOMAIN
- Invalid or malformed domain input — returns DNS error
- Domain does not exist — NXDOMAIN response
- Network or Cloudflare DoH upstream timeout — service unavailable error
- Payment failure (x402 protocol) — request not processed

## How this service works

SMTP service discovery (_smtp._tcp.<domain>): SRV records with priority, weight, port and target host, from Cloudflare DoH. Tells a client where the domain's smtp service lives without guessing hosts. $0.01 per lookup.

## Output

Returns SRV record data for _smtp._tcp.<domain> including one or more records each with priority (integer), weight (integer), port number, and target hostname, sourced from Cloudflare DoH. If no SRV record exists, returns an empty or NXDOMAIN response.

## 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/smtp-srv-record-lookup-via-cloudflare-doh-9e341a99/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)