# MailTester Ninja (remote · mcp.mailtester.ninja)

Verify email addresses live against their mail server and find work emails. Nothing stored.

- Trust score: 83/100 (high trust)
- Change this week: +10
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- remote · `mcp.mailtester.ninja`: 83/100 (this document), [markdown](https://verifymcp.io/servers/ninja-mailtester-email-verification/mcp.md), [page](https://verifymcp.io/servers/ninja-mailtester-email-verification/mcp)

## Channel facts

- Endpoint: `https://mcp.mailtester.ninja/mcp`
- Transports: `streamable-http`
- Auth: `required`
- Version: `1.0.1`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-11-05.

- **Endpoint Security**: 95/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation is enforced on tool calls, advertised via RFC 9728 protected-resource metadata. Discovery is public, which costs nothing: no tool can be invoked without a token.
  - HTTPS is enforced; there's no plaintext access path.
  - HSTS check failed: the Strict-Transport-Security header is absent.
  - DNSSEC is configured correctly; the domain's records validate against the full chain to the root.
  - The authorisation server supports Client ID Metadata Documents, the current MCP client-registration mechanism.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 71/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 480 tokens (~240/item across 2 items; 2 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 27/100
  - Stability observed for 8 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
  - Structured output schemas are declared (100% of tools); any adoption earns full credit.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 2 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 3 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

## Install

### How do I install the MailTester Ninja MCP server?

MailTester Ninja is a hosted endpoint at https://mcp.mailtester.ninja/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http ninja-mailtester-email-verification 'https://mcp.mailtester.ninja/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "ninja-mailtester-email-verification": {
      "url": "https://mcp.mailtester.ninja/mcp"
    }
  }
}
```

### VS Code

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

### Codex

```toml
[mcp_servers.ninja-mailtester-email-verification]
url = "https://mcp.mailtester.ninja/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "ninja-mailtester-email-verification": {
      "type": "remote",
      "url": "https://mcp.mailtester.ninja/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add ninja-mailtester-email-verification --url 'https://mcp.mailtester.ninja/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  ninja-mailtester-email-verification:
    url: "https://mcp.mailtester.ninja/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "ninja-mailtester-email-verification": {
      "Transport": "http",
      "Url": "https://mcp.mailtester.ninja/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add ninja-mailtester-email-verification -t streamable-http -u 'https://mcp.mailtester.ninja/mcp'
```

### Other

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

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-11-05 (score 83, +1)

No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-03 (score 82, +1)

No change was recorded against any check on this day. Stability & Change Management went from 17 to 20. That category is still filling its 30-day observation window: 5 days of observed history at the previous scan, 6 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-02 (score 81, +7)

- [security improvement] Authorization: partial → pass
- [security] First check of Authorization: pass
- [security] The server rewrote its instructions, which are the text every model session reads
- [security] Tool “find_email” rewrote its description, which is the text the model reads
- [functional regression] Schema quality: 193 → 240
- [functional] Server version: 1.2.1 → 1.4.0

### 2026-11-01 (score 74, 0)

- [security] The server rewrote its instructions, which are the text every model session reads
- [security] Tool “find_email” rewrote its description, which is the text the model reads
- [functional regression] Schema quality: 167 → 193
- [functional] Server version: 1.1.0 → 1.2.1
- [cosmetic] “find_email” reworded the description of “first_name”
- [cosmetic] “find_email” reworded the description of “last_name”
- [cosmetic] “find_email” dropped the optional parameter “middle_name”

### 2026-10-31 (score 74, +1)

- [functional] Server version: 1.0.1 → 1.1.0

### 2026-10-29 (score 73, +1)

- [functional improvement] Stability: unverified → 0.03

### 2026-10-28 (score 72)

First indexed and scored.

## MCP tools (2)

### `verify_email` (~80 tokens)

Verify an email address

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.

Input parameters:

- `email` (string, required): The email address to verify

Output parameters:

- `code` (string): "ok" valid, "ko" invalid, "mb" uncertain
- `domain` (string|null)
- `email` (string)
- `message` (string): Accepted, Rejected, Catch-All, No MX, Disposable, Timeout...
- `mx` (string)

### `find_email` (~180 tokens)

Find a professional email address

Find the work email address of a business contact, for professional outreach, from their first name, last name and company domain. The company's common address formats (first.last, flast, first, firstlast, first_last, f.last) are checked one by one with the company's own mail server, and the first one it accepts is returned. No database is searched and nothing is stored. Stops early when the domain accepts every address (catch-all) and then gives the most common format as "guess". Each format checked counts as one verification. Personal email providers such as gmail.com are refused. Requires a paid MailTester Ninja key.

Input parameters:

- `domain` (string, required): Company domain, for example example.com
- `first_name` (string, required): First name, for example Jean-Pierre
- `last_name` (string, required): Last name, for example De La Tour

Output parameters:

- `code` (string)
- `confidence`: For an address found: high (first and last name in it), medium (an initial, a namesake may share it), low (first name only)
- `email` (string|null): The address the mail server accepted, when found
- `format` (string|null): Pattern of the returned address: first.last, flast, first, firstlast, first_last or f.last
- `found` (boolean)
- `guess` (string|null): On a catch-all domain, the most common pattern; for a full mailbox, that address. Not verified.
- `message` (string)
- `reason` (string|null)
- `tested` (array): Every address checked, in order, with its verdict
- `tried` (integer): Number of address patterns checked, each one counted as a verification

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/ninja-mailtester-email-verification/mcp#diagnostics

## Score history

- 2026-11-05: 83
- 2026-11-04: 82
- 2026-11-03: 82
- 2026-11-02: 81
- 2026-11-01: 74
- 2026-10-31: 74
- 2026-10-30: 73
- 2026-10-29: 73
- 2026-10-28: 72

## Common questions

### What is the MailTester Ninja MCP server?

MailTester Ninja is an MCP server listed in the public MCP registry as ninja.mailtester/email-verification. Verify email addresses live against their mail server and find work emails. Nothing stored. This page covers its hosted endpoint (https://mcp.mailtester.ninja/mcp).

### Is the MailTester Ninja MCP server safe to use?

MailTester Ninja scores 83 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the MailTester Ninja MCP server expose?

MailTester Ninja exposes 2 tools: verify_email, find_email. Their descriptions and schemas cost roughly 260 tokens of context every time the server is loaded.

### Does the MailTester Ninja MCP server require authentication?

Yes. MailTester Ninja asked us for credentials when we connected, so you will need to authorise it in your MCP client before it can do anything.

### Is the MailTester Ninja MCP server still maintained?

MailTester Ninja is still listed as active in the MCP registry. We last reached this channel on 5 November 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

### What did VerifyMCP test on the MailTester Ninja MCP server?

VerifyMCP ran 13 checks on MailTester Ninja, covering TLS certificate, Authorization, HTTPS, HSTS header and 9 more. Supply Chain Security and Provenance & Transparency do not apply to a hosted endpoint, so they were not tested. The score does not measure everything, and the scoring documentation lists what it leaves out.

## Links

- Remote endpoint: https://mcp.mailtester.ninja/mcp
- Authorisation metadata: https://mcp.mailtester.ninja/.well-known/oauth-protected-resource/mcp
- Website: https://mailtester.ninja/integrations/mcp/
- Changelog RSS feed: https://verifymcp.io/servers/ninja-mailtester-email-verification/mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/ninja-mailtester-email-verification/mcp/changelog.json
- Trust report (JSON): https://verifymcp.io/servers/ninja-mailtester-email-verification/mcp.json
- HTML version of this page: https://verifymcp.io/servers/ninja-mailtester-email-verification/mcp