I Built an Email Verification API That Costs $0 to Run

#mcp #email #node #api

Last week I shipped an MCP server that validates email addresses. No third-party APIs. No per-request fees. Just DNS lookups.

It's called Email Verify MCP and it's my 62nd open-source tool on Smithery.

How most email verification works (expensive)

Services like ZeroBounce, NeverBounce, and Hunter charge $0.008–$0.01 per verification. If you're onboarding 100,000 users, that's $800–$1,000 just to check emails. These services resell DNS lookups with a markup.

What I built instead

Email Verify MCP does the same thing using raw DNS queries:

MX record check — does the domain accept mail?
SMTP handshake — can the mailbox actually receive?
Disposable domain detection — flags temp emails from services like Mailinator
Role account detection — catches admin@, noreply@, support@

Zero API costs. It runs locally or as an MCP server your AI agent can call.

{
  "email": "user@gmail.com",
  "valid": true,
  "disposable": false,
  "role_account": false,
  "mx_records": ["gmail-smtp-in.l.google.com"],
  "smtp_checked": true
}

Why this matters for agents

AI agents need to send emails. Before they do, they should verify the recipient exists. A single SMTP handshake takes < 200ms and prevents bounce-backs that poison your domain reputation.

The MCP protocol means any agent framework (Claude, Cursor, Windsurf) can call this tool with a natural language prompt: "Check if user@example.com is a real address."

The tech stack

Node.js — single file, no framework
DNS module — built into Node, no dependencies
SMTP — handshake-only, no email sent
MCP SDK — @modelcontextprotocol/sdk for the server interface
Smithery — one-click install for 500,000+ developers

Total dependencies: 1 (the MCP SDK).

The business model

Free tier: 50 verifications/day
Pro tier: 1,000/month for $19/mo

I'm targeting solo founders and indie devs who need email validation but can't justify $100+/mo for enterprise tools. If even 30 people sign up, that's $570/mo on infrastructure that costs $0.