MAILTYPE

Email/domain → objective mail capability intelligence.

MAILTYPE is a tiny REST + MCP API for applications that need fast, objective domain-level email infrastructure answers before accepting, storing, routing, or acting on an email address.

Live API: https://mailtype-api.onrender.com/docs
OpenAPI: https://mailtype-api.onrender.com/openapi.json
Playground: https://mailtype-api.onrender.com/play?q=gmail.com
MCP endpoint: https://mailtype-api.onrender.com/mcp

What it returns

• DOMAIN_EXISTS

• CAN_RECEIVE_MAIL

• MX records and provider

• disposable-domain evidence

• SPF

• DMARC

• MTA-STS

• confidence, evidence, and checked_at

Related MCP server: mailX tools

Why MAILTYPE

MAILTYPE deliberately does not perform SMTP probing or claim that an individual mailbox exists. It answers the cheaper, objective domain-level questions that software often needs first. UNKNOWN is a valid answer whenever the evidence is insufficient.

REST

curl -H "X-API-Key: YOUR_KEY" \
  https://mailtype-api.onrender.com/v1/domain/gmail.com

curl -H "X-API-Key: YOUR_KEY" \
  https://mailtype-api.onrender.com/v1/email/person@gmail.com

MCP

Endpoint: POST https://mailtype-api.onrender.com/mcp

Tool: inspect_mail_domain

Input:

{"input":"gmail.com"}

Public discovery endpoints

• Docs: https://mailtype-api.onrender.com/docs

• Playground: https://mailtype-api.onrender.com/play?q=gmail.com

• OpenAPI 3.1: https://mailtype-api.onrender.com/openapi.json

• Sources and methodology: https://mailtype-api.onrender.com/sources

• Health: https://mailtype-api.onrender.com/health

Data and standards

MAILTYPE uses DNS evidence plus a maintained legally reusable disposable-domain dataset. The API exposes its methodology and source disclosure publicly. Relevant standards include RFC 5321, RFC 7505 (Null MX), RFC 7208 (SPF), RFC 7489 (DMARC), and RFC 8461 (MTA-STS).

Hard boundary

MAILTYPE does not verify that a mailbox exists, connect to recipient SMTP servers, send email, infer deliverability from opaque scores, or claim CAN_RECEIVE_MAIL=YES without explicit MX evidence. If a domain exists but explicit MX evidence is insufficient, MAILTYPE returns UNKNOWN.

Stranger Verification Standard

Our own tests, health probes, validators, uptime traffic, and known internal callers do not count as adoption. A tool call alone does not automatically become a verified stranger; outside calls remain unverified until evidence supports credible real use.

Keywords

email API · domain API · MX lookup API · disposable email domain API · SPF API · DMARC API · MTA-STS API · email infrastructure · email validation preflight · MCP server · developer API