# ProbeKit MX Record Lookup

> ProbeKit MX Record Lookup is a paid API for AI agents from api.probekit.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-30).

Lists a domain's mail servers in preference order and detects null MX (RFC 7505) and unresolvable MX targets with coded findings.

## Facts

- Endpoint: GET https://api.probekit.dev/v1/mail/mx?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/probekit-mx-record-lookup-cd157229
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_O00td-qVkJwE6dHHpS3Db

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 probekit-mx-record-lookup-cd157229
```

Example prompt: Can you look up the MX records for probekit.dev and tell me which mail servers handle its email, whether any of them fail to resolve, and if the domain has a null MX set?

## When to prefer this

Use this endpoint when you need to specifically inspect mail server configuration for a domain — either to route email correctly, diagnose delivery failures, or detect domains that have opted out of receiving mail via null MX. Prefer this focused MX endpoint over the full mail diagnostics report when you only need MX data and want lower cost and faster response. Use the sibling bulk endpoint when checking more than one domain at once.

## Known failure modes

- Domain does not exist (NXDOMAIN) — returns error or empty MX result
- Domain has no MX records — returns empty list, possibly with null MX flag
- MX target hostnames do not resolve — flagged as coded findings in response
- Malformed or overly long domain input — rejected by schema validation
- Temporary DNS resolver failure — may return transient error
- Payment failure or missing x402 credentials — request rejected before processing

## How this service works

List a domain's mail servers in preference order and detect null MX (RFC 7505) and MX targets that do not resolve, with coded findings. Use when an agent must find where mail for a domain is delivered or why a domain cannot receive mail.

## Output

Returns an ordered list of MX records for the domain including hostname and priority, a flag indicating whether a null MX (RFC 7505) is present, and coded diagnostic findings for any MX targets that fail DNS resolution.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "title": "DomainInput",
     "required": [
      "domain"
     ],
     "properties": {
      "domain": {
       "type": "string",
       "title": "Domain",
       "examples": [
        "example.com"
       ],
       "maxLength": 1024,
       "minLength": 1
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/probekit-mx-record-lookup-cd157229/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.probekit.dev](https://www.zero.xyz/host/api.probekit.dev/llms.txt)