io.github.kryptoscanPublished by GitHub account kryptoscanv0.1.0Updated Oct 29, 2026
Check SPF, DKIM, DMARC, blocklists, reverse DNS and email headers against Gmail/Yahoo sender rules.
Read-only MCP server that diagnoses email deliverability: SPF, DKIM, DMARC, blocklists, reverse DNS and received headers.
Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.
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.kryptoscan%2Femail-deliverability-mcp/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.Add this to your client's mcpServers config.
{
"mcpServers": {
"email-deliverability-checker": {
"type": "http",
"url": "https://api.ownmailserver.com/tools/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.
A hosted copy runs at:
Add it to Claude as a custom connector (Settings → Connectors → Add custom connector), or in Claude Code:
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.
Requires Node.js 20 or later.
Claude Code
Claude Desktop (claude_desktop_config.json)
Docker
BLOCKLIST_DNS mattersSpamhaus 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.
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_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.Authentication-Results header, which is what the recipient's mailbox provider concluded, and the newest Received hop that names the sending server.example.co.uk). It's not a full Public Suffix List lookup, so unusual suffixes may be misjudged.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.
MIT
Source: README.md at commit 5981484
Check a domain's email DNS
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.
domainrequireddkim_selectorsCheck a 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.
iprequiredCheck 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: Show original).
headersrequired100% 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.
https://api.ownmailserver.com/tools/mcpclaude mcp add --transport http email-deliverability https://api.ownmailserver.com/tools/mcpclaude mcp add email-deliverability -- npx -y email-deliverability-mcp{ "mcpServers": { "email-deliverability": { "command": "npx", "args": ["-y", "email-deliverability-mcp"] } }}docker build -t email-deliverability-mcp .docker run -i --rm email-deliverability-mcpnpm installnpm test # unit tests with a fake DNS resolvernpm run build # compiles to dist/npm run start:http # the HTTP version (PORT, MCP_PATH, TRUST_PROXY, RATE_LIMIT, GLOBAL_LIMIT)