Email Deliverability Checker

Name: Email Deliverability Checker
Author: kryptoscan

by kryptoscanversion 0.1.0i★ –iRuns in the cloud

Registry nameio.github.kryptoscan/email-deliverability-mcp

Install

Overview

Description from the maker (original English)

Check SPF, DKIM, DMARC, blocklists, reverse DNS and email headers against Gmail/Yahoo sender rules.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi3 of 3 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs in the cloud
Transport: Streamable HTTP
Category: Chat & email

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 3 of 3 passed
Runs on the maker’s server: what you ask it goes through their server.
Can do 3 things (tools) check_domain, check_sending_ip, check_email_headers
The registry lists no key to fill in.

You need

Runs in the cloudNothing to install; it connects over the internet

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Works in Claude on the web, desktop and mobile:

Open Settings → Connectors
Press Add custom connector
Paste the address below and press Add
If it asks you to sign in, sign in with the maker

https://api.ownmailserver.com/tools/mcp

Run this in your terminal

claude mcp add --transport http email-deliverability https://api.ownmailserver.com/tools/mcp

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "email-deliverability": {
      "url": "https://api.ownmailserver.com/tools/mcp"
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "email-deliverability": {
      "type": "http",
      "url": "https://api.ownmailserver.com/tools/mcp"
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

ChatGPT connects only to servers on the internet:

Open ChatGPT on the web → Settings → Connectors (Apps)
Press Create or Add (some plans need Developer mode under Advanced first)
Paste the address below, give it a name and save
If it asks you to sign in, sign in with the maker

https://api.ownmailserver.com/tools/mcp

Menu names can differ slightly by plan and over time.

Your choice stays on this device in a cookie; no account needed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Tool names and descriptions exactly as the server reported them on Nov 7, 2026. The maker wrote them, not us; we show them as plain text.

check_domain
Check a domain's SPF (including the 10-DNS-lookup limit), DMARC policy and reporting, DKIM keys on common selectors, and MX records. Returns problems ranked by severity with the fix for each, plus the email services the domain uses.
check_sending_ip
Check a mail server's IP: reverse DNS (PTR) and whether it resolves back to the IP, and listings on Spamhaus ZEN, Barracuda, SpamCop, PSBL, Mailspike and UCEPROTECT level 1. A refused Spamhaus query is reported as unknown, never as a listing.
check_email_headers
Check a received email's headers against Gmail's and Yahoo's bulk sender requirements: SPF, DKIM and DMARC results, From domain alignment, one-click unsubscribe (and whether DKIM covers it), TLS, reverse DNS and Message-ID. Use the full headers as the recipient got them (Gmail: S

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account kryptoscan, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
✓ Pass
Endpoint responds
Responded in 336 ms (HTTP 200)
– Not applicable
Sign-in with OAuth
No sign-in needed
✓ Pass
No hidden instructions in tool descriptions
Read 3 tool descriptions and found no hidden instructions to the AI

Compared with others in Chat & emaili

More stars than 0% of the other 1787 servers in this category
Published to the registry more recently than 71% of the other 1787 servers in this category
Basic checks equal to or better than 100% of the other 1787 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Email Deliverability Checker safe?

It passed 3 of 3 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.

Is it still maintained?

The GitHub repo last changed –, and the latest version (0.1.0) reached the registry 11 days ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT in developer mode.

What can I use instead?

In the same category: Vexa, emailmd, MCP WhatsApp Cloud

Alternatives

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Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

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Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

email-deliverability-mcp

An MCP server that lets Claude (or any MCP client) diagnose email deliverability:

`check_domain`: SPF (including the 10-DNS-lookup limit), DMARC policy and reporting, DKIM keys on common selectors, and MX records, with a ranked list of problems and the fix for each. It also names the email services a domain uses (Google Workspace, SendGrid, Amazon SES and others).
`check_sending_ip`: reverse DNS (PTR) and whether it resolves back to the IP, plus listings on Spamhaus ZEN, Barracuda, SpamCop, PSBL, Mailspike and UCEPROTECT level 1.
`check_email_headers`: paste a received message's headers and check them against Gmail's and Yahoo's sender requirements: SPF, DKIM, DMARC, From alignment, one-click unsubscribe (and whether DKIM covers it), TLS, reverse DNS and Message-ID.

Every tool is read-only: it reads public DNS or the text you give it. Nothing is sent anywhere else, and no account or API key is needed.

Use it without installing

A hosted copy runs at:

https://api.ownmailserver.com/tools/mcp

Add it to Claude as a custom connector (Settings → Connectors → Add custom connector), or in Claude Code:

claude mcp add --transport http email-deliverability https://api.ownmailserver.com/tools/mcp

It's free and needs no account. It's rate-limited per IP, uses public DNS resolvers (so Spamhaus results show as "refused"; see below), and stores nothing. For heavy use or a real Spamhaus answer, run your own copy.

Install

Requires Node.js 20 or later.

Claude Code

claude mcp add email-deliverability -- npx -y email-deliverability-mcp

Claude Desktop (claude_desktop_config.json)

"mcpServers": { "email-deliverability": { "command": "npx", "args": ["-y", "email-deliverability-mcp"] } } }

Docker

docker build -t email-deliverability-mcp .

docker run -i --rm email-deliverability-mcp

Things to ask

"Check example.com's email setup and tell me what to fix first."
"Why might our emails from shop.example be going to spam?" (then paste a message's headers)
"Is 192.0.2.25 on any blocklists? Does its reverse DNS look right?"
"Does this email meet Gmail's bulk sender rules?"
"Our SPF record fails sometimes. Are we over the lookup limit?"

Configuration

Variable	Default	What it does
`BLOCKLIST_DNS`	the system resolver	Comma-separated IPs of a recursive resolver you run, used for blocklist lookups.
`DNS_SERVERS`	the system resolver	Comma-separated resolver IPs for all other lookups.

Why `BLOCKLIST_DNS` matters

Spamhaus refuses queries that arrive through big public resolvers (8.8.8.8, 1.1.1.1 and the like) and answers 127.255.255.x instead. Many blocklist checkers misread that as "listed". This server reports it as refused, meaning unknown, and says so. To get a real Spamhaus answer, point BLOCKLIST_DNS at a recursive resolver of your own, such as unbound on 127.0.0.1.

How the checks work

SPF lookups follow include: and redirect= recursively and count every include, a, mx, ptr, exists and redirect term, as RFC 7208 does. More than 10 is a permanent error at most receivers.
DKIM keys sit under selectors that only the sender knows, so the server probes about 30 common ones. Pass your own with dkim_selectors (find it in the s= value of a message's DKIM-Signature header). Domains that answer every name (wildcard DNS) are detected and not reported as having keys.
Header checks read the topmost Authentication-Results header, which is what the recipient's mailbox provider concluded, and the newest Received hop that names the sending server.
Alignment compares organizational domains with a simple rule (the last two labels, or three for names like example.co.uk). It's not a full Public Suffix List lookup, so unusual suffixes may be misjudged.

Development

npm install

npm test # unit tests with a fake DNS resolver npm run build # compiles to dist/ npm run start:http # the HTTP version (PORT, MCP_PATH, TRUST_PROXY, RATE_LIMIT, GLOBAL_LIMIT)

About

Built by OwnMailServer, which runs dedicated email sending for businesses that send 250,000 to 1,000,000 emails a month: your own server and IP, a Resend-style API and SMTP, managed warm-up and daily monitoring. OwnMailServer accounts also get a Claude connector for their own sending data: delivery stats, bounces, complaints and message history.

The same checks are available as free web tools: the email health checker and the bulk sender checker.

License

MIT

Email Deliverability Checker

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Chat & emaili

Common questions

Alternatives

Vexa

emailmd

MCP WhatsApp Cloud

README from the maker

email-deliverability-mcp

Use it without installing

Install

Things to ask

Configuration

Why BLOCKLIST_DNS matters

How the checks work

Development

About

License

Why `BLOCKLIST_DNS` matters