
MailboxValidator
- 1 repo stars
- Updated June 3, 2026
- MailboxValidator/mcp-mailboxvalidator
MailboxValidator MCP is an MCP server that checks email addresses through the MailboxValidator API from your coding agent.
About
MailboxValidator MCP is a stdio Model Context Protocol server that exposes the MailboxValidator email validation API to coding agents such as Claude Code and Cursor. Developers use it while they are still in the validate phase—especially on landing pages, waitlists, and early signup prototypes—so agents can verify whether an address is likely deliverable before you store it or trigger welcome sequences. The published server manifest describes one npm package at version 1.0.0 with a required secret MAILBOXVALIDATOR_API_KEY, which keeps setup straightforward: install the server, add the key to your MCP config, and invoke validation from natural-language tasks rather than copying validation snippets into every stack. It is a narrow integration focused on address checks, not full marketing automation or list hygiene at scale. Pair it with your own form backend or no-code embed; the value is consistent, API-backed validation inside the same workspace where you are iterating copy and scope.
- Stdio MCP server (npm mcp-mailboxvalidator v1.0.0) that calls the MailboxValidator API from the agent
- Validates single email addresses via MCP tools instead of hand-rolling regex in every form handler
- Requires MAILBOXVALIDATOR_API_KEY as a secret environment variable on the server package
- Fits agent-driven flows: check an address while drafting landing copy, form schemas, or CRM import steps
- MCP integration, not a hosted form product—you bring the API key and your capture surface
MailboxValidator by the numbers
- Data as of Jul 7, 2026 (Skillselion catalog sync)
claude mcp add --env MAILBOXVALIDATOR_API_KEY=YOUR_MAILBOXVALIDATOR_API_KEY mcp-mailboxvalidator -- npx -y mcp-mailboxvalidatorAdd your badge
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| repo stars | ★ 1 |
|---|---|
| Package | mcp-mailboxvalidator |
| Transport | STDIO |
| Auth | Required |
| Last updated | June 3, 2026 |
| Repository | MailboxValidator/mcp-mailboxvalidator ↗ |
What it does
Wire real-time email validation into your agent so waitlist and signup flows reject typos and disposable addresses before they hit your database.
Who is it for?
Best when you're wiring waitlists, betas, or lead magnets and already use MailboxValidator (or will get an API key) and want validation inside Claude Code or Cursor.
Skip if: Skip if you need bulk list cleaning, CRM sync, or compliance workflows without bringing your own MailboxValidator account and API limits.
What you get
Your agent can validate addresses on demand during build-out of forms and flows, so fewer bad emails get committed before you scale traffic or connect ESPs.
- Agent-callable email validation results backed by MailboxValidator
- Configured stdio MCP server entry with secret API key handling
- Fewer invalid addresses committed during landing and signup implementation
By the numbers
- Server manifest version 1.0.0
- 1 npm stdio package (identifier mcp-mailboxvalidator)
- 1 required secret environment variable: MAILBOXVALIDATOR_API_KEY
README.md
MailboxValidator MCP server
This is a simple Model Context Protocol (MCP) server implementation for MailboxValidator API. It will return validation result for an email address.
Features
- Comprehensive Email Validation: Checking an email address to see if an email is reachable by checking the syntax, DNS, MX server, high risk, suppressed list, and more.
- Disposable Email: Checking an email address to see if it's from a temporary/disposable email provider.
- Free Email: Checking an email address to see if it's from a free email provider.
Requirement
This MCP server requires an API key. You can also sign up for a free API key and enjoy up to 300 queries per month.
The setup also uses Node.js and npm, which can be downloaded at Node.js website.
Setup
Follow the steps to use this MCP server with Claude Desktop:
- Download the repository to your local.
- Run the following commands while inside the project folder to install dependencies and build the server.
npm install
npm run build
- Make sure you have installed Claude Desktop. If you haven't, kindly download from here for Windows and macOS users, or follow this guide for Linux users.
- Open
claude_desktop_config.json. If you don't have that file yet, follow this guide to create one. - Add the following to your
claude_desktop_config.json:
{
"mcpServers": {
"mailboxvalidator": {
"command": "node",
"args": [
"C:\\path\\to\\mcp-mailboxvalidator\\build\\index.js"
],
"env": {
"MAILBOXVALIDATOR_API_KEY": "<YOUR_API_KEY>"
}
}
}
}
- Remember to replace the path for the
index.jswith your actual path to your MailboxValidator MCP server on your local machine. - To get your API key, just login to your dashboard and get it from there. Replace the
<YOUR_API_KEY>in the above with your actual API key. - Restart the Claude Desktop after saving the changes, and you should see it appear in the
Search and toolsmenu.
Usage
Just enter your query about the email address in a chat in Claude Desktop. Some of example queries are:
- Is (email) a valid email address?
- Is (email) a fake email?
- Is (email) a free email?
In Claude Desktop, the model will automatically generate the output based on the result returned by MailboxValidator MCP server.
Environment Variable
MAILBOXVALIDATOR_API_KEY
The free MailboxValidator API key allows you to query up to 300 emails per month. If you require more, you can sign up for a paid API plan.
Tool
validate_email
Description Validates the email address given. It helps users to determine if an email address is potentially reachable by checking the syntax, DNS, MX server, disposable list and more.
Arguments email (str): The email address to validate.
Returns A JSON string containing the validation data. The result includes the following fields:
- Syntax: Checks that the email address conforms to how an email address should look like.
- DNS & MX Server: Checks that the domain DNS has an MX server specified.
- Network & Connectivity: Attempts connection to the MX server to make sure it's operational.
- Greylisting: Checks if MX server is using greylisting that could cause email sent to that address to bounce.
- Disposable List: Checks if the email domain is from a temporary or disposable email provider.
- High Risk & Suppressed List: Checks if email username looks high-risk or if the email address is found in a suppression list.
- Others: Checks the reputation score for the email and more..
If the request fails, the tool will return an error message as a string.
check_disposable_email
Description Checks if the email address given is from a disposable email provider.
Arguments email (str): The email address to check.
Returns A JSON string containing the disposable email data. The result includes the following fields:
- Disposable List: Checks if the email domain is from a temporary or disposable email provider.
If the request fails, the tool will return an error message as a string.
check_free_email
Description Checks if the email address given is from a free email provider.
Arguments email (str): The email address to check.
Returns A JSON string containing the free email data. The result includes the following fields:
- Free Email List: Checks if the email domain is from a free email provider.
If the request fails, the tool will return an error message as a string.
License
See the LICENSE file.
Recommended MCP Servers
How it compares
MailboxValidator API exposed as MCP tools—not a form builder, ESP, or agent skill for copywriting.
FAQ
Who is MailboxValidator MCP for?
Developers and small teams using AI coding agents who need API-backed email validation while designing landing and signup flows, not marketers running batch list audits only in a dashboard.
When should I use MailboxValidator MCP?
Use it during validate-phase landing and prototype work whenever you add email fields, import CSV leads, or debug why signups look inflated with junk addresses.
How do I add MailboxValidator MCP to my agent?
Register the npm stdio server mcp-mailboxvalidator in your agent’s MCP config, set the required MAILBOXVALIDATOR_API_KEY secret, restart the client, and call the server’s validation tools from your session.