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Mail Tester Ninja MCP server

Which MCP servers are Mail Tester Ninja's own, from the official registry and from asking its own domain, whether they answer, and what they offer. A program checked each of these, nobody copied them from a product page.

read 2026-10-29

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Whose server it is
  • Registry nameninja.mailtester/email-verificationverified in the MCP registry

The registry name sits under mailtester.ninja. The registry only lets a publisher use that namespace after proving control of the domain through DNS or HTTP.

When we asked itchecked 2026-10-29
  • Stateanswerschecked 2026-10-29
  • Tools2
  • Server calls itselfmailtester-ninja
  • Server version1.0.1
  • Protocol version2025-06-18

On 2026-10-29 the server answered initialize and tools/list without a sign-in. First answer in 524 ms.

Should an agent connect itConnect it
  • Its tools do every use case we checked: confirm a single address is deliverable before sending; remove invalid addresses from a mailing list before a campaign; locate missing addresses for outreach contacts.

Once connected

  • For "confirm a single address is deliverable before sending", the likely first call is verify_email.
  • For "remove invalid addresses from a mailing list before a campaign", the likely first call is verify_email.
  • For "locate missing addresses for outreach contacts", the likely first call is find_email.

Said by rules from the measurements above. The likely first call is a model's pick from the tool list; read its description before relying on it.

Measured dailydaily checks: 7, the first on 2026-10-29
  • INITE MCP score100 of 100answers 100 · does the job 100 · definitions 100 · context 100 · connects 100
  • What an agent can do with it3 of 3 use cases
  • Answered100% of days7 of 7 daily checks
  • Median first answer514 ms
  • Space in an agent's context≈ 417 tokensthe definitions of all its tools (2), which an agent carries on every turn
  • Tool definitionsA · 100 of 100
  • Typed results2 of 2 toolsdeclared outputSchema: results come typed, read once
  • Every tool passes all six checks.

What an agent can do with it

  • can do · confirm a single address is deliverable before sending
  • can do · remove invalid addresses from a mailing list before a campaign
  • can do · locate missing addresses for outreach contacts

Each of the product's use cases, put to Jev against this server's tool list: can an agent do it with these tools?

Worth a look

None of the five warning signs in these definitions.

A program checks the server once a day: initialize and tools/list, no model. Tokens are the definitions' length at about four characters a token. The grade averages six checks of every tool's name, description, schema and annotations; it says how well the tools are described, not whether they work. The score weighs what was measured and nothing else: answering (25%), doing the product's job (25%), definitions (20%), context (10%), use (10%) and how readily a client connects (10%). A part that was not measured is left out, and a hidden instruction caps the score at 40. The state of vendors' MCP servers: method and numbers →

Tools it offers2 tools · read 2026-10-29
  • verify_email

    Check in real time whether an email address exists and can receive mail, by asking the recipient's mail server (no message is sent). Returns code "ok" (valid), "ko" (invalid) or "mb" (uncertain, such as a catch-all domain) with a message.

  • find_email

    Find the work email address of a person from their name and their company domain. Tries the usual patterns (first.last, flast, first...) one by one and returns the first address the mail server accepts. Each pattern tried counts as one…

How to connect

Add the server to your MCP client config. Claude Desktop, Cursor and most other clients read this shape:

{
  "mcpServers": {
    "email-verification": {
      "type": "http",
      "url": "https://mcp.mailtester.ninja/mcp"
    }
  }
}

Add it

Claude Code, in a terminal

claude mcp add --transport http mailtester https://mcp.mailtester.ninja/mcp

Add to CursorAdd to VS Code

claude.ai, ChatGPT and other clients: add https://mcp.mailtester.ninja/mcp as a custom connector in the settings.

OpenAPI spec

1 paths, read 2026-10-29. Open the spec ↗

Each line is something a program found when it went looking: the registry entry, the server's own answer, a spec that parses. A missing line means we did not find it, not that it does not exist.