MCP Mailboxvalidator

What MailboxValidator/mcp-mailboxvalidator MCP server does

MailboxValidator/mcp-mailboxvalidator MCP server connects an MCP-compatible client to the MailboxValidator API. It accepts an email address and returns validation data as a JSON string. The full validation response can cover syntax, domain DNS, MX server presence, network connectivity, greylisting, disposable-email status, high-risk indicators, suppression-list status, reputation, and related checks.

The server also exposes narrower checks. One identifies whether an address belongs to a temporary or disposable email provider, while another checks whether its domain is associated with a free email provider. These separate tools are useful when an application needs only one classification rather than the broader validation response.

Tools and capabilities

The available tools are:

• validate_email: validates one email address and returns a JSON string containing the available validation results.
• check_disposable_email: checks whether the address uses a disposable email provider.
• check_free_email: checks whether the address uses a free email provider.

Each tool takes an email string argument. If a request fails, the tool returns an error message as a string. The README does not describe batch validation, bulk imports, write operations, or additional inputs.

How it works

The MCP client sends an email address to one of the server tools. The server uses the configured MailboxValidator API key to request the corresponding result from MailboxValidator, then returns the response to the client as JSON text. With validate_email, the returned data can include checks for address syntax, DNS and MX configuration, connectivity to the mail server, greylisting, disposable providers, high-risk or suppressed addresses, and reputation.

MailboxValidator/mcp-mailboxvalidator MCP server is suited to agent workflows that need to ask questions such as whether an address appears valid, fake, disposable, or associated with a free email provider. The README specifically demonstrates use with Claude Desktop, where the model can generate a response from the tool result.

Setup and configuration

The documented setup requires Node.js and npm. After downloading the repository, install its dependencies and build it from the project directory:

npm install
npm run build

Configure the client to launch the generated build/index.js file with Node. The configuration must provide the MAILBOXVALIDATOR_API_KEY environment variable. The API key can be obtained from the MailboxValidator dashboard; the README also links to a free plan.

A free API key supports up to 300 queries per month according to the README. Higher usage requires a paid MailboxValidator plan. After saving the client configuration, restart Claude Desktop so the server appears in its tools interface.

Limitations and notes

The server depends on an external MailboxValidator API and therefore requires a valid API key. Results and request failures are returned by the tools as strings rather than being described as a richer MCP-specific schema in the README. The documented client setup uses a local source checkout and a built JavaScript entry point; no hosted endpoint or package-manager installation command is provided.

MailboxValidator/mcp-mailboxvalidator MCP server does not document authentication methods other than the MAILBOXVALIDATOR_API_KEY environment variable. The README includes a LICENSE file reference but does not state the license name in the supplied material.