# Domain Intel — MX Fastmail Lookup

> Domain Intel — MX Fastmail Lookup is a paid API for AI agents from dns.halowerk.com, paid per call via x402, $0.009/call, status unknown (last checked 2026-10-13).

Checks whether a domain's MX records point to Fastmail, optionally comparing against a baseline snapshot, and returns full domain intelligence including WHOIS, DNS, mail policy, TLS certificate, and subdomains.

## Facts

- Endpoint: POST https://dns.halowerk.com/domain/articles/mx-fastmail?utm_source=zero.xyz
- Price: $0.009/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/domain-intel-mx-fastmail-lookup-237236a4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ybL-FaD_QwqNReu1XOC8y

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 domain-intel-mx-fastmail-lookup-237236a4 -d '<json body>'
```

Example prompt: Check if acme.com uses Fastmail for email — pull its MX records, WHOIS, DNS, TLS certificate, and subdomains, and compare the MX against this baseline: mx1.messagingengine.com (priority 10), mx2.messagingengine.com (priority 20), observed on 2024-01-15.

## When to prefer this

Choose this endpoint when you specifically need to verify or monitor Fastmail MX record presence for a domain alongside comprehensive domain intelligence (WHOIS, DNS, TLS, subdomains) in a single pay-per-call request with no signup. Prefer it over generic WHOIS or DNS APIs when Fastmail-specific mail routing verification is the primary goal, or when you need to diff current MX state against a stored baseline. It is ideal for lightweight, one-off agent tasks where recurring API keys are impractical and micropayment via USDC is acceptable.

## Known failure modes

- Invalid or non-existent domain returns an error or empty result set
- Domain with no MX records returns null mail policy data
- Baseline schema mismatch (missing required fields: domain, observed_at, records) causes validation error
- Payment failure over x402 prevents the call from completing
- DNS resolution timeout for slow or obscure TLDs may produce partial results
- MX priority values outside 0–65535 or exchange hostnames over 254 characters are rejected

## How this service works

Requires an unauthenticated caller-owned baseline; returns real current NS/MX records, added/removed sets and tri-state target-provider transition. Current DNS comes from one bounded native recursive-resolver query; existing Dossier provides context. Resolver caching may apply; no account ownership or global migration-completion claim. Existing provider patterns are reused without new invented attribution. At most50records,domain253chars,9sbudget; DNSsubquery2s/oneattempt. Unknown provider remai

## Output

Returns a comprehensive domain intelligence report covering WHOIS registration data, full DNS record set, MX records with Fastmail match status, SPF/DKIM/DMARC mail policy, TLS certificate details, and discovered subdomains. If a baseline is provided, includes a comparison indicating whether MX records have changed since the observed timestamp.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "domain": {
   "type": "string",
   "maxLength": 253
  },
  "baseline": {
   "type": "object",
   "required": [
    "domain",
    "observed_at",
    "records"
   ],
   "properties": {
    "domain": {
     "type": "string",
     "maxLength": 253
    },
    "records": {
     "type": "array",
     "items": {
      "type": "object",
      "required": [
       "exchange",
       "priority"
      ],
      "properties": {
       "exchange": {
        "type": "string",
        "maxLength": 254
       },
       "priority": {
        "type": "integer",
        "maximum": 65535,
        "minimum": 0
       }
      },
      "additionalProperties": false
     },
     "maxItems": 50
    },
    "observed_at": {
     "type": "string",
     "maxLength": 40
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/domain-intel-mx-fastmail-lookup-237236a4/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from dns.halowerk.com](https://www.zero.xyz/host/dns.halowerk.com/llms.txt)