MX Record Lookup
Query the MX records for any domain via DNS-over-HTTPS: every mail exchanger with its priority, sorted so the primary (lowest number) comes first. The definitive check for 'can this domain receive email' before sending anything.
🔌 Server-side tool
This tool runs on the server (it fetches third-party URLs directly and cannot run in your browser). Use the paid JSON API below — the worked examples show real server-side results and refresh automatically.
Worked examples
Google's mail routing
GET /api/v1/security/mx-lookup?domain=gmail.com
Result: gmail.com → gmail-smtp-in.l.google.com, alt1.gmail-smtp-in.l.google.com, alt2.gmail-smtp-in.l.google.com, alt3.gmail-smtp-in.l.google.com, alt4.gmail-smtp-in.l.google.com
Microsoft 365 tenant
GET /api/v1/security/mx-lookup?domain=microsoft.com
Result: microsoft.com → microsoft-com.mail.protection.outlook.com
No-mail domain
GET /api/v1/security/mx-lookup?domain=example.com
Result: example.com →
Machine API (x402)
$0.002 / callThis tool is also a JSON API for AI agents. Requests without payment receive 402 Payment Required plus instructions; agents pay USDC on Base via the x402 protocol — no accounts, no API keys.
GET /api/v1/security/mx-lookup?domain=gmail.com HTTP/1.1
Host: agentstoolshub.com
→ 402 (payment required, instructions in headers)
→ 200 (after X-PAYMENT header; JSON body below)
{
"tool": "security/mx-lookup",
"input": {"domain":"gmail.com"},
"result": { "value": 5, "answer": "gmail.com → gmail-smtp-in.l.google.com, alt1.gmail-smtp-in.l.google.com, alt2.gmail-smtp-in.l.google.com, alt3.gmail-smtp-in.l.google.com, alt4.gmail-smtp-in.l.google.com" }
}Agent docs: /llms.txt · OpenAPI spec · integration guide
About this tool
Authoritative MX records for any domain, live over DNS-over-HTTPS and sorted by routing priority. Before an agent sends mail on a domain's behalf — or validates a business contact — this answers whether the domain can receive mail at all and through which provider.
Frequently asked questions
What does MX priority mean?
Lower numbers are tried first. Senders attempt the lowest-priority-value host and fall back to higher ones — so the first row is the domain's primary mail route.
What if a domain has no MX?
Per RFC 5321 senders fall back to the domain's A/AAAA record, but many will simply bounce. No MX for a 'business' domain is a strong signal about its email hygiene.