✉️Email Validator
Validate an email address in two layers: strict RFC-style syntax, then a live DNS MX lookup on the domain to confirm the recipient actually runs mail servers. Catches the typos and fake domains that pure regex misses.
Worked examples
Gmail address
GET /api/v1/dev/email-validator?email=someone%40gmail.com
Result: ✓ Deliverable — mail handled by gmail-smtp-in.l.google.com.
Corporate domain
GET /api/v1/dev/email-validator?email=info%40microsoft.com
Result: ✓ Deliverable — mail handled by microsoft-com.mail.protection.outlook.com.
Nonexistent domain
GET /api/v1/dev/email-validator?email=user%40this-domain-does-not-exist-12345.com
Result: ✗ Domain "this-domain-does-not-exist-12345.com" cannot receive email
Machine API (x402)
$0.001 / 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/dev/email-validator?email=someone%40gmail.com HTTP/1.1
Host: agenttools-hub.vercel.app
→ 402 (payment required, instructions in headers)
→ 200 (after X-PAYMENT header; JSON body below)
{
"tool": "dev/email-validator",
"input": {"email":"someone@gmail.com"},
"result": { "value": 1, "answer": "✓ Deliverable — mail handled by gmail-smtp-in.l.google.com." }
}Agent docs: /llms.txt · OpenAPI spec · integration guide
About this tool
Two-layer validation: strict syntax first, then a live MX lookup proving the domain actually operates mail servers (with the implicit-A/AAAA fallback from RFC 5321). This catches fake domains and the typos regex-only checks wave through.
valid = syntax ∧ (MX ∃ ∨ A/AAAA ∃) — with the lowest-priority MX as the mail host
Frequently asked questions
Does a positive result guarantee delivery?
No — it proves the domain can receive mail. Whether the specific mailbox exists is only knowable by sending (or an SMTP-level probe, which many providers block).
Why check A records when there's no MX?
RFC 5321 implicit MX: domains without MX records must still accept mail at their A/AAAA address. Skipping that check would reject valid addresses.