mcpField
M
MX Probe

MX Probe

Local
mxprobe.devCommunication2Updated 5w ago
RepositoryVisit website

About MX Probe

MX Probe checks email addresses and returns a `send`, `hold`, or `kill` decision with a reason. It is for agents and developers validating recipients, with local DNS checks and an optional hosted SMTP probe.

Key features

  1. 01Syntax and DNS checks
  2. 02Hosted SMTP mailbox probing
  3. 03Three-way verdict with explanation
  4. 04Batch email verification
  5. 05API signup and credit management

Use cases

  1. 01Screen recipient lists before sending
  2. 02Hold uncertain addresses for fallback handling
  3. 03Verify addresses in batches
  4. 04Check remaining hosted-probe credits

MCP support

The `mxprobe mcp` command runs an MCP server over stdio. It exposes email verification, batch verification, signup, balance, and credit-purchase tools; verification uses the hosted tier when a key is configured and otherwise uses local DNS checks.

Configuration

Local server config is the same for every client. Copy it into your client’s MCP config file.

mcp.json · Universal config
{
  "mcpServers": {
    "dev-mxprobe-mxprobe": {
      "command": "npx",
      "args": [
        "-y",
        "mxprobe"
      ],
      "env": {
        "MXPROBE_API_KEY": "<MXPROBE_API_KEY>"
      }
    }
  }
}
Run commandnpx -y mxprobe
Environment variables to set
MXPROBE_API_KEYSecretHosted-tier API key from POST /v1/signup or the signup tool. Without it the verify tools run the free local DNS tier.

Local servers need a runtime on your machine (e.g. Node.js 18+). Config file locations differ by client; see your client’s docs.

Packages
npmmxprobe0.2.6

Tools

5

Saved tool list · updated 2w ago

ParameterTypeRequiredDescription
emailstringYesThe address to check
hostedbooleanNoProbe the mailbox on the hosted tier (default: yes when a key is configured)

Details

From the project README

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 [email protected] [email protected]   # free, local, no key
npx mxprobe signup [email protected]                    # a key by API, 100 free checks, saved to ~/.config/mxprobe
npx mxprobe check --hosted [email protected]          # 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": "[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 }
}
  • 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(["[email protected]"], { 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.

Comments

Markdown supported

New to MCP?

From what the protocol is to installing your first server, these answers cover most first questions.

An open protocol that defines how AI applications connect to external tools and data in a uniform way. Clients talk to the model; MCP servers provide tools, resources and prompt templates. They exchange standard messages, so one server can be reused by many clients.