mxprobe

Email verification for AI agents. One call returns send, hold or kill with the reason. The DNS tier is free and runs on your machine; the hosted SMTP probe is 9 USD per 10,000 checks, 100 free at signup.

npx mxprobe check hello@example.com ops@example.org   # free, local, no key
npx mxprobe signup you@company.com                    # a key by API, 100 free checks, saved to ~/.config/mxprobe
npx mxprobe check --hosted hello@example.com          # DNS kills stay local; survivors go to the mailbox probe
npx mxprobe balance
npx mxprobe buy                                       # a Stripe link: 9 USD per 10,000, credits never expire
npx mxprobe mcp                                       # the MCP server on stdio

MCP

claude mcp add mxprobe -- npx -y mxprobe mcp

One click: Cursor · VS Code · LM Studio. In Claude Code, as a plugin: /plugin marketplace add andrewchmr/mxprobe, then /plugin install mxprobe@mxprobe.

Any client: {"mcpServers":{"mxprobe":{"command":"npx","args":["-y","mxprobe","mcp"]}}}

Tools: verify_email, verify_batch, signup, balance, buy_credits. With a key configured, verify_* probe the mailbox on the hosted tier; without one they run the free DNS tier. Set MXPROBE_API_KEY to use a key from the environment.

Verdict

{
  "email": "hello@example.com",
  "action": "send",
  "verdict": "OK",
  "reason": "mailbox accepted by aspmx.l.google.com",
  "checks": { "syntax": true, "mx": "aspmx.l.google.com", "smtp": "accepted", "catch_all": false }
}

• send: the mail server accepted the mailbox.
• hold: send only with a fallback in hand. A catch-all, a forwarder, a greylist, or a server that refused the probe rather than the mailbox.
• kill: never send. No mail server, or the mailbox does not exist.

From Node

import { createClient, checkEmails } from "mxprobe";
const client = createClient({ apiKey: process.env.MXPROBE_API_KEY });
const { results, summary } = await checkEmails(["a@b.com"], { hosted: true, client });

Typed: Client, CheckOptions, CheckOutput and the response types come with the package; results is VerifyResult[] from mxprobe-core.

Docs: https://mxprobe.dev. Source: https://github.com/andrewchmr/mxprobe. MIT.