DemiSignal MCP server

Ask your AI assistant to check a domain’s SPF, DKIM and DMARC, or to write the SPF and DMARC records it is missing. Free, with no account and no API key.

Connect

One address, any MCP client.

https://demisignal.com/mcp

A remote server over streamable HTTP. There is nothing to install.

Claude (claude.ai and the desktop app)

Settings → Connectors → Add custom connector. Name it DemiSignal, paste the address above and leave the authentication settings empty.

Claude Code

claude mcp add --transport http demisignal https://demisignal.com/mcp

Cursor, Windsurf and other clients

Add it to the client’s MCP settings file:

{
  "mcpServers": {
    "demisignal": { "url": "https://demisignal.com/mcp" }
  }
}

VS Code

In .vscode/mcp.json:

{
  "servers": {
    "demisignal": { "type": "http", "url": "https://demisignal.com/mcp" }
  }
}

Tools

Three tools, all read-only.

check_domain: Reads a domain’s DMARC, SPF, DKIM, MX, BIMI and MTA-STS records from public DNS, fetches the MTA-STS policy and BIMI logo they point to, and grades each one, with the issues found and a guide for each. The same check as the free domain check.
generate_spf_record: Builds an SPF record from the services and servers that send your email, with an estimate against the 10 DNS lookup limit. The same record as the SPF record generator.
generate_dmarc_record: Builds a DMARC record and the host to publish it at, from a policy and your reporting addresses. The same record as the DMARC record generator.

Try: “Check the email authentication for example.com and tell me what to fix first.”

Privacy

Only what you ask it to check.

Your assistant sends DemiSignal only the domain you ask about, or the options for a record. Each domain check is kept for 180 days, so its report link shows exactly what was seen; the generators keep nothing. The IP address your assistant connects from is used to share the free checks fairly between everyone using them. You are never asked who you are. Details are in the privacy policy.

Questions, answered

Before you connect it.

Do I need an account or an API key?

No. Add the server address to your AI client and the three tools are ready to use.

Is there a limit?

New checks are shared by everyone using the server, up to a daily allowance. When it runs out, a domain checked in the last few minutes still answers, and other domains can be checked again the next day (UTC) or on the website.

Does it change my DNS?

No. check_domain only reads: it looks up public DNS records and fetches the MTA-STS policy and BIMI logo they point to. The generators only return a record for you to publish yourself.