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The MailBeast MCP server lets an AI assistant work in your workspace: create campaigns, add leads, check mailboxes and warmup, read and answer replies, and pull analytics - by asking in plain language.
It uses the same API key as the REST API, with the same scopes, plan access (Pro+ and enterprise) and rate limit - tool calls count against it like direct API requests. The assistant only sees the tools your key’s scopes allow - a read-only key gets read-only tools.
Create a separate key for MCP in Settings → API Keys. You can revoke it at any time without touching your other integrations.

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Connect

The server speaks Streamable HTTP. Pass the key as a header, or - for apps that only take a URL - in the path.

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What the assistant can do

Every tool calls the matching endpoint of the REST API (see the API Reference tab) - the MCP server adds no extra permissions.

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Safety

  • Real email is marked for confirmation. start_campaign, resume_campaign, send_test_email, reply_to_email and forward_email are marked as acting on the outside world, and deletions as destructive. Claude and ChatGPT typically ask you before running such tools - unless you chose to always allow them.
  • Campaigns are created as drafts. Starting is always a separate step, so the assistant can show you the sequence and send you a test email first.
  • An email is never sent twice by a retry. Calling reply_to_email, forward_email or send_test_email again with exactly the same arguments within 24 hours returns the first result (alreadyDone: true) - a dropped connection can’t send it twice. To send the same test email again on purpose, the assistant passes a new resend value. Other tools simply run again, which is harmless for them (pausing twice, adding a lead that already exists). See Idempotency.
  • Passwords. Prefer start_oauth_connect for Google Workspace and Microsoft 365 mailboxes - it needs no password. SMTP/IMAP passwords passed to connect_mailboxes are stored encrypted and never returned.

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Example prompts

  • “How many emails can I still send this month?”
  • “Create a 3-step campaign for SaaS founders in Berlin, weekdays 9-17 their time, and send me a test of step 1.”
  • “Which mailboxes are failing and why?”
  • “Show me today’s interested replies and draft answers.”
  • “Compare reply rates of my last three campaigns.”
https://developer.mailbeast.ai/mcp is a different server: it searches this documentation and does not touch your workspace. It’s useful for agents that write code against the API.