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MailTester Email Verification

Official registry Productivity

Verify emails (valid/invalid/risky/unknown): MX, SMTP, catch-all, disposable. Free agent key.

Source code Website Documentation

Install

Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).

Remote (streamable-http)
Claude Code 
claude mcp add --transport http mailtester-email-verification 'https://app.mailtester.com/mcp' --header 'Authorization: <Bearer <api_key>. Get a free key (25 verifications/day) with the get_api_key tool or POST https://app.mailtester.com/agent-gateway/register>'
JSON configuration (Claude Desktop, Cursor, VS Code) 
{
    "mcpServers": {
        "mailtester-email-verification": {
            "type": "http",
            "url": "https://app.mailtester.com/mcp",
            "headers": {
                "Authorization": "<Bearer <api_key>. Get a free key (25 verifications/day) with the get_api_key tool or POST https://app.mailtester.com/agent-gateway/register>"
            }
        }
    }
}

Documentation

From the project's README on GitHub, refreshed weekly. Links open on GitHub.

Contents
  1. MailTester MCP server — email verification for AI agents
  2. Get a key (no account needed)
  3. Connect
  4. Tools
  5. Verdicts
  6. Limits
  7. REST API

MailTester MCP server — email verification for AI agents

Remote Model Context Protocol server that tells an AI agent whether an email address can receive mail before anything is sent to it.

The server is hosted; there is nothing to install. This repository documents how to connect.

Get a key (no account needed)

Connect without a key and call the get_api_key tool, or:

curl -X POST https://app.mailtester.com/agent-gateway/register \
  -H 'Content-Type: application/json' \
  -d '{"name":"my-agent","purpose":"verify signup emails"}'

The key is shown once. Each key gets 25 free verifications per day (unused credits do not roll over) and expires after 30 days; register again when it does. Send it as Authorization: Bearer <api_key>.

Connect

Claude Code

claude mcp add --transport http mailtester https://app.mailtester.com/mcp --header "Authorization: Bearer YOUR_KEY"

Claude Desktop / Cursor / VS Code (mcp.json-style config)

{
  "mcpServers": {
    "mailtester": {
      "type": "http",
      "url": "https://app.mailtester.com/mcp",
      "headers": { "Authorization": "Bearer YOUR_KEY" }
    }
  }
}

Tools

ToolWhat it does
get_api_keyGet a free key (works without a key)
verify_emailVerify one address → valid, invalid, risky or unknown (1 credit)
verify_batchVerify up to 25 addresses per call, with per-address verdicts
get_batch_status, list_lists, get_listFollow saved verification lists
explain_resultExplain a verdict in plain English, with a send recommendation
estimate_cost, get_credit_balanceCheck credits before running

Verdicts

  • valid: the mailbox exists and accepts mail
  • invalid: the address or domain cannot receive mail
  • risky: accept-all (catch-all) domain, role or disposable address, or a Microsoft 365 address the mail server couldn't confirm
  • unknown: the receiving server gave no definitive answer

Limits

10 requests per minute per key, one request in flight per key, and a shared daily capacity for free agent keys (HTTP 429 until 00:00 UTC when it is used up). Inbox placement, blacklist monitoring and email finder need a full account at https://mailtester.com.

REST API

The same key works on the REST API: POST https://app.mailtester.com/api/v1/verify, POST https://app.mailtester.com/api/v1/verify/batch, GET https://app.mailtester.com/api/v1/credits. See the OpenAPI description.

Frequently asked questions

What is MailTester Email Verification?

Verify emails (valid/invalid/risky/unknown): MX, SMTP, catch-all, disposable. Free agent key.

How do I install MailTester Email Verification?

It runs as a remote server. In Claude Code: claude mcp add --transport http mailtester-email-verification 'https://app.mailtester.com/mcp' --header 'Authorization: <Bearer <api_key>. Get a free key (25 verifications/day) with the get_api_key tool or POST https://app.mailtester.com/agent-gateway/register>'. For other clients, paste the JSON configuration from this page into their MCP settings.

Does MailTester Email Verification need an API key?

Yes. It expects Authorization, which you set in its configuration.

Is MailTester Email Verification open source?

Its code is public on GitHub, but the repository does not declare a standard license.

Who maintains MailTester Email Verification?

It is published by mailtester-com. AI.tn lists it but does not maintain or endorse it.

From the official MCP Registry. Listing is not an endorsement: review a server's code and permissions before giving it access to your data.