MailTester Ninja
REMOTE · MCP.MAILTESTER.NINJA
Verify email addresses live against their mail server and find work emails. Nothing stored.
Available components
Last scanned (12 hours ago)
Scores higher than 87% of remote servers
Reachable. Last reached 5 Nov 2026.
Category CRM and Sales
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. How we score → Why this is hard to score →
Endpoint Security95
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- 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. View diagnostics → Pass
- HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
- HSTS check failed: the Strict-Transport-Security header is absent. See how to fix → View diagnostics → Fail
- DNSSEC is configured correctly; the domain's records validate against the full chain to the root. View diagnostics → Pass
- The authorisation server supports Client ID Metadata Documents, the current MCP client-registration mechanism. View diagnostics → Pass
Transport & Reachability100
- Verified streamable-http transport via a live MCP handshake. View diagnostics → Pass
Schema Quality & AI Usability71
- AI-judged instruction clarity (excellent).Pass
- 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. See how to fix → Fail
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management27
- Stability observed for 8 of 30 days with no destabilising changes; credit accrues until the full window elapses.Partial
Tool Coverage100
- 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
- 100% of tool parameters carry a description.Pass
- Structured output schemas are declared (100% of tools); any adoption earns full credit.Pass
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 2 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 3 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
- Implements a current MCP spec version (2026-07-28).Pass
Checks we ran (13)
- TLS certificate
- Authorization
- HTTPS
- HSTS header
- DNSSEC
- Transport
- Schema quality
- Stability
- Tool coverage
- Injection markers
- Destructive annotations
- Judged manipulation
- MCP protocol
Does not apply to this hosted endpoint (2)
- Supply Chain SecurityScored on package channels only. This is a hosted endpoint, so there is nothing to install or inspect.
- Provenance & TransparencyScored on package channels only. This is a hosted endpoint, so there is nothing to install or inspect.
The score does not measure everything. What the score does not measure →
Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.
- 5 Nov 26 +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.
- 3 Nov 26 +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.
- 2 Nov 26 +7
- 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 security
- Schema quality: 193 → 240 ▼ functional
- Server version: 1.2.1 → 1.4.0 functional
- 1 Nov 26 0
- 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 security
- Schema quality: 167 → 193 ▼ functional
- Server version: 1.1.0 → 1.2.1 functional
- “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” cosmetic
- 31 Oct 26 +1
- Server version: 1.0.1 → 1.1.0 functional
- 29 Oct 26 +1
- Stability: unverified → 0.03 ▲ functional
- 28 Oct 26 72
First indexed and scored.
Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.
Captured 5 Nov 2026 · Probed https://mcp.mailtester.ninja/mcp
TLS valid
Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .
| Subject | Issuer | Valid from | Valid until | Key | Signature | Serial |
|---|---|---|---|---|---|---|
| CN=mcp.mailtester.ninja | CN=YE2,O=Let's Encrypt,C=US | 28 Oct 2026 | 26 Jan 2027 | ECDSA 256 | ECDSA-SHA384 | 6a9c138e23b74bfc2c8097ab90077ccc8ce |
| SANs: mcp.mailtester.ninja | ||||||
| CN=YE2,O=Let's Encrypt,C=US (CA) | CN=Root YE,O=ISRG,C=US | 3 Sept 2025 | 2 Sept 2028 | ECDSA 384 | ECDSA-SHA384 | 4df3b15dd6c0784c507cd37b58e6f115 |
| CN=Root YE,O=ISRG,C=US (CA) | CN=ISRG Root X2,O=Internet Security Research Group,C=US | 13 May 2026 | 2 Sept 2032 | ECDSA 384 | ECDSA-SHA384 | 872165fc34b6e5fba8add5b3705fb53a |
| CN=ISRG Root X2,O=Internet Security Research Group,C=US (CA) | CN=ISRG Root X1,O=Internet Security Research Group,C=US | 13 May 2026 | 2 Sept 2032 | ECDSA 384 | SHA256-RSA | 6c8f1dc727c7117f7baf853ac980f9cd |
Background: What to check on a remote MCP endpoint →
DNSSEC secure
Validation of mcp.mailtester.ninja. — Secure
| Zone | DS | Keys | Algorithms | Outcome |
|---|---|---|---|---|
| . | Trust anchor | 20326, 38696 | 8, 8 | Verified |
| ninja. | DS published | 46082 | 8 | Verified |
| mailtester.ninja. | DS published | 49385 | 8 | Verified |
| mcp.mailtester.ninja. | Verified address RRset verified with the apex keys |
Authentication Enforced and verified
The endpoint asked for a token and published valid RFC 9728 metadata describing how to get one.
| Result | Enforced and verified |
|---|---|
| Enforced | On tool calls |
| HTTP status | 200 |
WWW-Authenticate challenge Bearer error="invalid_token", error_description="A MailTester Ninja key is required for this tool. Sign in to connect yours.", resource_metadata="https://mcp.mailtester.ninja/.well-known/oauth-protected-resource/mcp", scope="verify"
Bearer error="invalid_token", error_description="A MailTester Ninja key is required for this tool. Sign in to connect yours.", resource_metadata="https://mcp.mailtester.ninja/.well-known/oauth-protected-resource/mcp", scope="verify"Protected resource metadata
| Document | https://mcp.mailtester.ninja/.well-known/oauth-protected-resource/mcp |
|---|---|
| Retrieved | Yes |
| Resource | https://mcp.mailtester.ninja/mcp |
| Authorisation server | https://mcp.mailtester.ninja |
Background: How OAuth 2.1 works in the 2026 MCP spec →
Transports 2 probes
| Transport | URL | Outcome | Status | Location |
|---|---|---|---|---|
| streamable-http | https://mcp.mailtester.ninja/mcp | Verified | 200 | |
| http (plaintext) | http://mcp.mailtester.ninja/mcp | HTTPS enforced | 308 | https://mcp.mailtester.ninja/mcp |
The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →
find_email Find a professional email address ~180
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.
| Name | Type | Req | Description |
|---|---|---|---|
| domain | string | yes | Company domain, for example example.com |
| first_name | string | yes | First name, for example Jean-Pierre |
| last_name | string | yes | Last name, for example De La Tour |
| Name | Type | Req | Description |
|---|---|---|---|
| code | string | yes | – |
| confidence | – | yes | For an address found: high (first and last name in it), medium (an initial, a namesake may share it), low (first name only) |
| string|null | yes | The address the mail server accepted, when found | |
| format | string|null | yes | Pattern of the returned address: first.last, flast, first, firstlast, first_last or f.last |
| found | boolean | yes | – |
| guess | string|null | yes | On a catch-all domain, the most common pattern; for a full mailbox, that address. Not verified. |
| message | string | yes | – |
| reason | string|null | yes | – |
| tested | array | yes | Every address checked, in order, with its verdict |
| tried | integer | yes | Number of address patterns checked, each one counted as a verification |
No examples provided.
verify_email Verify an email address ~80
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.
| Name | Type | Req | Description |
|---|---|---|---|
| string | yes | The email address to verify |
| Name | Type | Req | Description |
|---|---|---|---|
| code | string | yes | "ok" valid, "ko" invalid, "mb" uncertain |
| domain | string|null | yes | – |
| string | yes | – | |
| message | string | yes | Accepted, Rejected, Catch-All, No MX, Disposable, Timeout... |
| mx | string | yes | – |
No examples provided.
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.
remote · mcp.mailtester.ninja
claude mcp add --transport http ninja-mailtester-email-verification 'https://mcp.mailtester.ninja/mcp'
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.