How do I install MX Probe?

Copy the stdio config for Cursor, Claude Desktop, Claude Code, or VS Code on this page. It uses the publisher's install, not a PlugMCP proxy.

Does MX Probe need an API key?

The publisher lists these environment variables: MXPROBE_API_KEY.

What transport does MX Probe use?

MX Probe runs locally over stdio.

When was MX Probe last checked?

Last checked 2026-10-16. Email verification for AI agents: send, hold or kill with the reason. Signup and credits by API.

MX Probe MCP server

Add this server

The publisher's own command. Not a PlugMCP endpoint.

Credentials from the publisher

MXPROBE_API_KEY — Hosted-tier API key from POST /v1/signup or the signup tool. Without it the verify tools run the free local DNS tier.

Provider

Add in Claude

Claude Code

MXPROBE_API_KEY=<secret> claude mcp add dev.mxprobe-mxprobe -- npx -y [email protected]

Run in a terminal.

Claude Desktop

{
  "mcpServers": {
    "dev.mxprobe-mxprobe": {
      "command": "npx",
      "args": [
        "-y",
        "[email protected]"
      ],
      "env": {
        "MXPROBE_API_KEY": "<secret>"
      }
    }
  }
}

claude_desktop_config.json

Step-by-step: add this in Claude

Remote URL or a command on your machine? How the two installs differ

MX Probe

Email verification for AI agents. One call returns send, hold or kill for an address, with the reason. Signup and credits happen by API too, so an outreach agent can provision itself. No form, no CAPTCHA, no dashboard.

Site and docs: https://mxprobe.dev
API: https://api.mxprobe.dev (it describes itself on GET /). OpenAPI: https://mxprobe.dev/openapi.json. For agents: https://mxprobe.dev/llms.txt
npm: mxprobe (CLI + MCP server), mxprobe-core (the engine)

npx mxprobe check [email protected]          # free DNS tier, local, no key
npx mxprobe check --hosted [email protected] # survivors go to the hosted SMTP probe
claude mcp add mxprobe -- npx -y mxprobe mcp # the MCP server

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

{
  "email": "[email protected]",
  "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 }
}

action is send, hold or kill; verdict is OK, WEAK or DEAD. A hold never becomes a kill on a refusal, a greylist or a catch-all. Only a 5xx that names the mailbox kills.

Layout

Path	What
`packages/core`	The engine: DNS tier, SMTP probe, the verdict contract and the API's wire types. Zero dependencies.
`packages/cli`	`npx mxprobe check
`server`	The hosted API: `node:http` + `node:sqlite`, Stripe Checkout, Resend, Telegram.
`site`	The landing page, static.
`deploy`	Caddyfile, systemd units, the install script and the runbook.

Develop

Everything is TypeScript (strict, ESM). Each package compiles its src/ to dist/ with tsc -b; the published packages ship dist/ only. mxprobe and the server import mxprobe-core through the workspace link to its dist/, so pnpm build at the root (which runs the packages in dependency order) must come before a single package's test or typecheck. Tests are .ts files that Node runs directly with its built-in type stripping.

pnpm install
pnpm build                      # tsc -b in each package, core first
pnpm test                       # builds, then: fake resolver, fake SMTP server, in-memory SQLite. No network.
pnpm typecheck                  # the sources and the tests, without emitting
pnpm test:live                  # the DNS tier against the real network
pnpm check [email protected]              # the CLI from this checkout
cp server/.env.example server/.env && pnpm dev:server

Node 22.18 or newer (24 recommended) to develop and to run the tests; the compiled engine and CLI run on Node 20, the server on 22.13 or newer (node:sqlite).

Pricing

100 checks free at signup, then 9 USD per 10,000, one payment, credits never expire. Addresses are logged for 24 hours for debugging and then deleted.

MIT.

MX Probe

Site and docs: https://mxprobe.dev
API: https://api.mxprobe.dev (it describes itself on GET /). OpenAPI: https://mxprobe.dev/openapi.json. For agents: https://mxprobe.dev/llms.txt
npm: mxprobe (CLI + MCP server), mxprobe-core (the engine)

npx mxprobe check [email protected]          # free DNS tier, local, no key
npx mxprobe check --hosted [email protected] # survivors go to the hosted SMTP probe
claude mcp add mxprobe -- npx -y mxprobe mcp # the MCP server

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

{
  "email": "[email protected]",
  "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 }
}

action is send, hold or kill; verdict is OK, WEAK or DEAD. A hold never becomes a kill on a refusal, a greylist or a catch-all. Only a 5xx that names the mailbox kills.

Layout

Path	What
`packages/core`	The engine: DNS tier, SMTP probe, the verdict contract and the API's wire types. Zero dependencies.
`packages/cli`	`npx mxprobe check
`server`	The hosted API: `node:http` + `node:sqlite`, Stripe Checkout, Resend, Telegram.
`site`	The landing page, static.
`deploy`	Caddyfile, systemd units, the install script and the runbook.

Develop

pnpm install
pnpm build                      # tsc -b in each package, core first
pnpm test                       # builds, then: fake resolver, fake SMTP server, in-memory SQLite. No network.
pnpm typecheck                  # the sources and the tests, without emitting
pnpm test:live                  # the DNS tier against the real network
pnpm check [email protected]              # the CLI from this checkout
cp server/.env.example server/.env && pnpm dev:server

Node 22.18 or newer (24 recommended) to develop and to run the tests; the compiled engine and CLI run on Node 20, the server on 22.13 or newer (node:sqlite).

Pricing

100 checks free at signup, then 9 USD per 10,000, one payment, credits never expire. Addresses are logged for 24 hours for debugging and then deleted.

MIT.

MX Probe

Add this server

Host a copy with our keys and logs.

Related MCP

Related skills

MX Probe

Layout

Develop

Pricing

MX Probe

Add this server

Host a copy with our keys and logs.

Related MCP

Related skills

MX Probe

Layout

Develop

Pricing