Email Spam Tester

io.github.serg-tanichevPublished by GitHub account serg-tanichevv1.0.0Updated Nov 2, 2026

Test an email before it goes out: a disposable address, 41 checks with RFC citations, a fix plan.

VerifiedStreamable HTTPWeb executableCommunication & CollaborationBusiness & Commerce

Overview

AI-generated overview

Remote MCP server for testing an email's deliverability: it hands out a disposable address, then returns a scored report with a fix plan.

What you can do
  • Reserve a single-use test address, optionally with provider placement, and get its report link
  • Wait for the analysis to finish and receive a summary of scores, failing and warning checks, and a fix plan
  • Read an existing report by its slug without waiting
  • Fetch the message exactly as delivered, with headers, both bodies and raw source
When to use it
Use it when you want to check a marketing or transactional email for spam and deliverability problems before sending it, and want an assistant to reserve the address, wait for the result and explain the fixes. It is less useful for mail sent from a personal laptop, since many checks read headers added by the sending platform.
Requirements
A remote streamable HTTP endpoint; nothing to install locally. No key or account is needed. Clients that do not speak streamable HTTP can bridge it with mcp-remote. The person must actually send a real message to the reserved address from the platform that will send the campaign.
Before you install
The report slug is the only access control: anyone holding it can read the report, including subject, sender, bounce address and full source, so do not test someone else's mail without asking. Message source is kept for an hour and then deleted. Provider placement uses some public test inboxes, so avoid confidential mail. A skip status is not a pass, and a score is optimistic while complete is false.

Installation

In SourceWeft

  1. Open Email Spam Tester in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/io.github.serg-tanichev%2Femail-spam-tester/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "email-spam-tester": {
      "type": "http",
      "url": "https://email-spam-tester.com/mcp"
    }
  }
}

README

Email Spam Tester MCP server

Email Spam Tester is a free, independent email deliverability testing tool built by Serhii Tanichev. This repository is the client side of its MCP server: how to connect an agent to it, what the tools do, and how to read what they return. There is nothing to install on a server; the MCP endpoint is hosted with the tool.

The service exposes an MCP server at https://email-spam-tester.com/mcp over streamable HTTP. No key, no account. The one-hour test works in every client:

ToolWhat it does
get_test_address(lang, include_placement=false)Reserves a disposable address and returns it with the slug and the report URL. lang decides the language of the fix plan a person sees on the report page. With include_placement the same send also shows which folder the message lands in at different mailbox providers: you get one list of recipients and a marker for the subject. Some of those inboxes are public test inboxes, so use it for mail that is not confidential.
wait_for_report(slug, timeout_seconds=150)Blocks until the analysis is done and returns a summary: scores, the failing and warning checks with their evidence, the fix plan. Nothing to poll and no sleep loop to get wrong.
get_report(slug)Reads an existing report without waiting.
get_message_source(slug)The message as delivered: headers in wire order, both bodies, the raw source. It is kept for an hour after it arrives, and in that hour anyone with the slug can read it; after that only the report remains.

get_report also returns provider placement so far, when the test asked for it.

In ChatGPT there is more, because ChatGPT tells the server which of its users is asking. Permanent mailboxes collect a series of letters (a welcome sequence, a newsletter) and check every one: open_series_mailbox(domain), list_series_mailboxes(), get_series_letters(mailbox_id), write_fix_plan(slug) and close_series_mailbox(mailbox_id). Other clients, Claude among them, are not offered these tools: a permanent mailbox belongs to someone, and they don't say who is asking. Every tool also returns structured content for an MCP Apps card (ui://widget/email-spam-tester-v3.html): the address with copy buttons that turns into the report when the mail lands. Clients that draw no card read the same result as text.

The agent's job in between is to send a real message to the address, from the platform that will send the campaign. Half the checks read headers the sending platform adds, so a copy sent from a laptop says little about it.

Claude plugin

This repository is also a Claude plugin and its own marketplace. In Claude Code:

bash
/plugin marketplace add serg-tanichev/email-spam-tester-mcp/plugin install email-spam-tester@email-spam-tester

The plugin is two things and nothing else. .mcp.json connects Claude to the remote server at https://email-spam-tester.com/mcp, and skills/email-spam-tester/SKILL.md tells Claude how to run a test: reserve an address, have the real message sent to it, wait for the report, fix, test again. There is no local code, no hook and no script. What leaves your machine is what the tools send to that server (a report slug, a language code, whether you asked for provider placement), and the email you choose to send to the test address. What the service keeps, and for how long, is in the privacy policy.

Claude Desktop

Add the server to claude_desktop_config.json (see claude-desktop.json for the whole file):

json
{  "mcpServers": {    "email-spam-tester": {      "url": "https://email-spam-tester.com/mcp"    }  }}

Clients that do not speak streamable HTTP directly can bridge it with mcp-remote:

json
{  "mcpServers": {    "email-spam-tester": {      "command": "npx",      "args": ["-y", "mcp-remote", "https://email-spam-tester.com/mcp"]    }  }}

ChatGPT

The ChatGPT plugin package (manifest, icons, review test cases) is in serg-tanichev/email-spam-tester-chatgpt-plugin. Until it is in the plugin directory you can add the server yourself: Plugins → Add → Create MCP App, server URL https://email-spam-tester.com/mcp, no authentication.

Claude Code

bash
claude mcp add --transport http email-spam-tester https://email-spam-tester.com/mcp

Reading what comes back

  • The per-check lines the tools return are in English whatever lang was set to; lang decides what the person opening the report URL sees.
  • A check status of skip is not a pass: the check did not apply. error means it could not run and is left out of the score.
  • complete: false means something could not be checked. Treat the score as optimistic until it is true.
  • The slug is the capability: whoever holds it can read the report, including the subject, the sender, the bounce address and the full source. Do not test somebody else's mail without asking.

The same instructions, written for an agent to read before it starts, are in SKILL.md, and in the project repository serg-tanichev/email-spam-tester.

Where it is listed

Files

  • claude-desktop.json: a complete Claude Desktop configuration with the server added.
  • server.json: the manifest in the MCP registry format, for registries and directories that read one.

License

MIT, see LICENSE. The license covers this repository, not the service.

Source: README.md at commit 4f2d7c2

Tools

4

get_test_address

Get a test address

Reserve a single-use address to send a draft email to, for a full check. Returns the address and the URL its report will appear at. The address accepts exactly one message and expires after an hour. The email has to be sent by the person, from the platform or mailbox they really send from: half the checks read what that platform adds. The report covers 42 checks (SPF, DKIM, DMARC, reverse DNS, TLS, blocklists, content, links, the Gmail and Yahoo bulk-sender rules) and a plan of what to fix. lang is decided now because the message arrives minutes later over SMTP, which carries no hint of who is waiting for it. What wait_for_report returns quotes check lines in English whatever it is set to; the person following report_url sees their own language.

Parameterslanginclude_placement

wait_for_report

Wait for the report

Wait until the message arrives and has been analysed, then summarise it. Call it after the email has been sent to the address from get_test_address. Blocks rather than returning "not ready yet": an agent told to poll writes a sleep loop and usually gives up before the analysis finishes. Provider placement keeps filling in for up to 30 minutes after the report; get_report reads the latest.

Parametersslugrequiredtimeout_seconds

get_report

Read a report

Read a report by its slug without waiting, with provider placement so far. The report stays at its link for good and anyone with the link can read it: the checks, the score, the fix plan, and the subject and sender of the email.

Parametersslugrequired

get_message_source

Read the received message

The message exactly as it was received: headers, both bodies, source. Useful when a finding points at a header and the agent needs to see what it actually sent rather than what it believes it sent. The message is kept for an hour after it arrives and then deleted; within that hour anyone with the slug can read it. After that only the report remains.

Parametersslugrequired

Version history

1
  1. v1.0.0LatestSep 17, 2026

Score

90% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts

    Declare a license in the repository or the registry entry.