# SRV Submission TCP Service Discovery

> SRV Submission TCP Service Discovery 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).

Looks up SRV DNS records for the SMTP submission service (_submission._tcp) of a domain via Cloudflare DoH, returning priority, weight, port, and target host.

## Facts

- Endpoint: GET https://dns.intel.rallylive.ca/dns/srv/submission-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/srv-submission-tcp-service-discovery-9fc1481d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UH2e03h-xbBn30jksZuV8

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 srv-submission-tcp-service-discovery-9fc1481d
```

Example prompt: Can you look up the _submission._tcp SRV DNS record for gmail.com and tell me the priority, weight, port, and target host for its email submission service?

## When to prefer this

Use this endpoint when you need to programmatically discover the SMTP submission service endpoint (host, port, priority, weight) for a given domain via standard SRV DNS records, particularly for email client auto-configuration or mail infrastructure validation. Prefer this over manual host guessing or MX record lookups when the domain is expected to publish a _submission._tcp SRV record. Use it over generic DNS resolvers when you want a clean, paid, per-lookup API with Cloudflare DoH reliability.

## Known failure modes

- Domain has no _submission._tcp SRV record — returns empty result or NXDOMAIN
- Invalid or malformed domain name input — may return error or empty response
- Cloudflare DoH upstream timeout or unavailability — returns error
- Non-existent domain queried — NXDOMAIN response
- Network connectivity issues to dns.intel.rallylive.ca — connection failure

## How this service works

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

## Output

Returns the SRV record set for _submission._tcp.<domain> including one or more records each with priority, weight, port number, and target hostname, sourced via Cloudflare DoH. If no SRV records exist, returns an empty or negative 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/srv-submission-tcp-service-discovery-9fc1481d/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)