# MX Record Lookup and Mail Server Check

> MX Record Lookup and Mail Server Check is a paid API for AI agents from domain-dns.x402tookit.com, paid per call via x402, $0.03/call, status unknown (last checked 2026-10-21).

Returns the mail servers (MX records) for a domain ordered by priority, with DNS resolution status for each host, and handles null-MX and implicit-MX edge cases.

## Facts

- Endpoint: GET https://domain-dns.x402tookit.com/mx-check?utm_source=zero.xyz
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/mx-record-lookup-and-mail-server-check-cfb2925d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_HGWfqc3ByQZ0m5itp2j6H

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 mx-record-lookup-and-mail-server-check-cfb2925d
```

Example prompt: What are the mail servers for stripe.com, listed by priority, and do they all resolve to real addresses?

## When to prefer this

Choose this endpoint when you specifically need MX record data — mail server hostnames, their DNS resolution status, priority ordering, and null-MX handling — rather than a full DNS record dump. It is more targeted than the all-records endpoint and more focused than the email address screen endpoint, making it ideal for mail routing validation, deliverability checks, and infrastructure audits where MX detail is the primary concern.

## Known failure modes

- Domain does not exist — returns empty MX array with appropriate verdict
- DNS timeout — may return degraded flag set to true
- Invalid domain input — missing or malformed domain query parameter
- Domain has null-MX record (RFC 7505) — returned as null host entry with explanation
- Domain relies on implicit MX (A record fallback) — noted in reasons

## How this service works

Mail servers of a domain by priority, whether each resolves to an address, and null-MX or implicit-MX handling.

## Output

Returns a structured object containing an array of MX records (each with host, priority, IPv4/IPv6 count, and a resolves boolean), a verdict string summarizing mail-readiness, a human-readable summary, an array of reasons explaining the verdict, flags for null-MX and degraded states, a timestamp, and optionally a source URL and disclaimer.

## 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",
     "required": [
      "domain"
     ],
     "properties": {
      "domain": {
       "type": "string",
       "description": "Domain name, e.g. gmail.com"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "mx": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "object",
        "properties": {
         "host": {
          "type": [
           "null",
           "string"
          ]
         },
         "ipv4": {
          "type": [
           "null",
           "number"
          ]
         },
         "ipv6": {
          "type": [
           "null",
           "number"
          ]
         },
         "priority": {
          "type": [
           "null",
           "number"
          ]
         },
         "resolves": {
          "type": [
           "boolean",
           "null"
          ]
         }
        }
       }
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "domain": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "sourceUrl": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      }
   
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mx-record-lookup-and-mail-server-check-cfb2925d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from domain-dns.x402tookit.com](https://www.zero.xyz/host/domain-dns.x402tookit.com/llms.txt)