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MailTester Email Verification MCP server

com.mailtester/email-verification

We checked this server on 2 November 2026 with McpStamp Check engine 1.2.0. It scored 75 of 100 (grade C), higher than 19.9% of the 33,003 registry servers that responded over HTTPS that day. Ready for MCP Registry. Not ready for Claude, ChatGPT and Gemini.

Measured facts

Score
75C
Sign-in
No sign-in
Tools listed
9
Protocol version
2024-11-05
Stores

Store readiness

StoreStatusReason
Claude Connectors Directory Not ready Blocked by readOnlyHint or destructiveHint on every tool and Human-readable title on every tool.
ChatGPT app directory Not ready Blocked by readOnlyHint or destructiveHint on every tool, Explicit readOnlyHint, destructiveHint and openWorldHint (ChatGPT) and Human-readable title on every tool.
Gemini Connected Apps Not ready Blocked by Supported protocol version negotiated.
Official MCP Registry Ready No blocking check failed.

MCP Registry ready means a valid public remote for the registry, not that the server is listed in a store.

Fixes

4 checks to fix

  1. Fails

    readOnlyHint or destructiveHint on every tool

    tool_annotations

    Blocks Claude and ChatGPT.

    Measured 9/9 tools set neither readOnlyHint nor destructiveHint: get_api_key, get_credit_balance, list_lists, get_list, explain_result and 4 more

    Set annotations.readOnlyHint: true on read-only tools and destructiveHint: true on tools that modify or delete data (Claude needs one of them on every tool; ChatGPT needs all three hints, see tool_open_world).

  2. Fails

    Supported protocol version negotiated

    protocol_version

    Blocks Gemini.

    Measured Negotiated 2024-11-05

    Return protocolVersion "2025-11-25" (or "2025-06-18") in the initialize result. Gemini Connected Apps requires 2025-03-26 to 2025-11-25.

  3. Fails

    Explicit readOnlyHint, destructiveHint and openWorldHint (ChatGPT)

    tool_open_world

    Blocks ChatGPT.

    Measured 9/9 tools miss an explicit hint: get_api_key, get_credit_balance, list_lists, get_list, explain_result and 4 more

    Set readOnlyHint, destructiveHint and openWorldHint to explicit true/false on every tool (OpenAI app review requires all three).

  4. Fails

    Human-readable title on every tool

    tool_titles

    Blocks Claude and ChatGPT.

    Measured 9/9 without title: get_api_key, get_credit_balance, list_lists, get_list, explain_result and 4 more

    Add a short human-readable "title" to every tool (shown in store UIs and consent screens).

13 checks passed, 10 did not run

Passed. Served over HTTPS, initialize over Streamable HTTP, JSON or SSE response Content-Type, JSON-RPC error for unknown method, GET answers SSE or 405, initialize latency, serverInfo name and version, Server instructions, tools capability declared, tools/list returns tools, inputSchema is an object schema, Tool names are valid and portable, Tool descriptions.

Not run. Sign-in method the store supports (OAuth or none), 401 carries WWW-Authenticate resource_metadata, Protected resource metadata (RFC 9728), Resource metadata "resource" equals the server URL, Authorization server metadata (RFC 8414 / OIDC), First metadata URL Gemini tries answers 200 with the required fields, issuer equals the authorization_servers entry; token_endpoint_auth_methods_supported (ChatGPT), PKCE S256 advertised, Client registration (DCR or Client ID Metadata Documents), refresh_token grant advertised. The server asks for no sign-in, so the OAuth checks do not apply.

Run a fresh check

This page is the 2 November 2026 snapshot. If you maintain this server and have shipped fixes since then, re-check it. The live check and the badge show the current result, and the next snapshot will pick up the change.

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McpStamp score for MailTester Email Verification

Markdown

[![McpStamp score](https://www.mcpstamp.com/badge?url=https%3A%2F%2Fapp.mailtester.com%2Fmcp)](https://www.mcpstamp.com/r/com-mailtester-email-verification/)

HTML

<a href="https://www.mcpstamp.com/r/com-mailtester-email-verification/"><img src="https://www.mcpstamp.com/badge?url=https%3A%2F%2Fapp.mailtester.com%2Fmcp" alt="McpStamp score" height="20"></a>
Registry entry

About this server

Verify emails (valid/invalid/risky/unknown): MX, SMTP, catch-all, disposable. Free agent key.
Registry name
com.mailtester/email-verification
Remote URL
https://app.mailtester.com/mcp
Version
1.0.1
Source
github.com/mailtester-com/mailtester-mcp
Website
app.mailtester.com/agent-gateway
Checked
2 November 2026, engine 1.2.0, no credentials

The description above is the server's own text from the official MCP Registry. If a result looks wrong, run a fresh check and email support@zovo.one with the report link.

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