Warm Inbox MCP server

Hosted Model Context Protocol server for Warm Inbox, an email warm-up and deliverability service. It lets AI assistants and app builders (Cursor, Claude Code, Lovable, Bolt, Replit, v0, Windsurf, Base44 and others) check warm-up health and spam rates, connect a mailbox through a secure hosted link, and pause, resume or tune daily sending volume.

• Endpoint: https://mcp.warminbox.org/mcp (Streamable HTTP, stateless)

• Auth: Authorization: Bearer wi_live_..., your own Warm Inbox API key from https://warminbox.org/public-api/keys.php

• Server card: https://mcp.warminbox.org/.well-known/mcp/server-card.json

• MCP Registry name: org.warminbox/mcp

• Privacy: https://warminbox.org/privacy-policy · Terms: https://warminbox.org/terms-of-service · Support: https://warminbox.org/contact-us

Safety

• The AI never handles mailbox passwords. New warm-ups are only created via create_connect_link: the AI shows a one-time URL (valid 30 minutes), and you enter SMTP/IMAP or Gmail credentials on Warm Inbox's hosted page. Tool schemas are strict and reject unknown fields such as passwords.

• The server stores nothing: no keys, sessions, database or request logs. Each request's bearer key is forwarded to the Warm Inbox REST API and discarded. Keys are redacted from upstream output.

• Requests without a valid-looking key get 401 with WWW-Authenticate: Bearer.

• Campaigns created in the Warm Inbox dashboard are visible but read-only.

Related MCP server: AI Agent Email List MCP Server

Tools

Successful JSON objects are returned unchanged in structuredContent and serialized text (apart from key redaction). This preserves {data:[...]} on lists, account/plan fields, warm-up source/read_only flags, nullable health metrics, and {url,expires_at} connect links. API {error:{code,message,...}} failures become isError:true with readable status/code/message text and structured error details. Network/timeout/invalid-JSON errors become generic tool errors. Timeout is 15 seconds; no automatic retries, since a write may have succeeded before the connection failed. Dashboard campaigns are read-only and writes return 404 or 403. Pause, resume and volume changes are reversible, non-destructive and idempotent; connect link creation is non-idempotent.

Optional prompt setup_warmup guides account confirmation, collecting non-secret fields, displaying the connect URL, waiting for the human, listing warm-ups and checking health.

Every tool has a human-readable title and full annotations (readOnlyHint, destructiveHint, idempotentHint, openWorldHint).

Client setup

Use endpoint https://mcp.warminbox.org/mcp and header Authorization: Bearer <your-own-wi_live_key>. Obtain a key at Warm Inbox API keys. Examples below contain placeholders only. Configure credentials privately in each app, never commit populated configuration or embed real keys in install links.

Documentation reviewed 2026-10-31. UI labels and plan availability can vary; items marked verify in-app could not be confirmed from accessible current official documentation.

Lovable

Add a custom MCP chat connector, name Warm Inbox, enter the endpoint, and choose bearer-token/API-key authentication. Set the token to your wi_live_... key; if the UI offers raw headers, use Authorization: Bearer .... Ask “Use Warm Inbox to list my warm-ups.” Custom MCP is builder context; it does not automatically install a runtime backend integration into the generated app. Official setup and authentication choices.

Bolt.new

Open Connectors, add a custom Connector, set URL to the endpoint and transport to HTTP. Select API-key authentication and supply your key so the outgoing header is Authorization: Bearer ... (exact field/prefix behavior: verify in-app). Bolt's official announcement confirms remote custom connectors and API-key/OAuth credentials. If this UI cannot emit a bearer header, this server cannot connect through that UI until OAuth is added.

Replit Agent

In Integrations → MCP Servers → Add MCP server, name Warm Inbox and enter the endpoint. Under Advanced settings add Authorization with value Bearer <your-own-wi_live_key>, then Test & save. Official custom-server guide.

Official Add to Replit link format: https://replit.com/integrations?mcp=<URL-encoded-base64-JSON>. Payload:

{"displayName":"Warm Inbox","baseUrl":"https://mcp.warminbox.org/mcp","headers":[{"key":"Authorization","value":"Bearer <your-own-wi_live_key>"}]}

For a public install link omit headers and ask the human to add the key privately after installation. Generate a key-free link locally:

const payload = { displayName: 'Warm Inbox', baseUrl: 'https://mcp.warminbox.org/mcp' };
console.log('https://replit.com/integrations?mcp=' + encodeURIComponent(Buffer.from(JSON.stringify(payload)).toString('base64')));

v0

Open MCP Connections (or the prompt form's MCP entry), add Warm Inbox and the endpoint. Set the Authorization bearer header if custom-header controls are available (verify in-app). Official MCP integrations page confirms both entrypoints; arbitrary bearer-header support was not confirmed. OAuth-only connection screens cannot use this server yet.

Windsurf

In ~/.codeium/windsurf/mcp_config.json:

{"mcpServers":{"warminbox":{"serverUrl":"https://mcp.warminbox.org/mcp","headers":{"Authorization":"Bearer <your-own-wi_live_key>"}}}}

Reload MCP servers in Cascade. Windsurf is now Devin Desktop; there, add the same url + headers block to .devin/config.json or ~/.config/devin/config.json.

Cursor

In .cursor/mcp.json (prefer private user configuration for real keys):

{"mcpServers":{"warminbox":{"url":"https://mcp.warminbox.org/mcp","headers":{"Authorization":"Bearer <your-own-wi_live_key>"}}}}

Enable the server in MCP settings. Official configuration. Official install deeplink:

cursor://anysphere.cursor-deeplink/mcp/install?name=warminbox&config=<URL-encoded-base64-JSON-config>

Use the official generator with the single-server config, or generate a link without credentials:

const config = { url: 'https://mcp.warminbox.org/mcp' };
console.log('cursor://anysphere.cursor-deeplink/mcp/install?name=warminbox&config=' + encodeURIComponent(Buffer.from(JSON.stringify(config)).toString('base64')));

After installation, add Authorization privately. Do not distribute bearer keys inside deeplinks.

Claude Code

claude mcp add --transport http warminbox https://mcp.warminbox.org/mcp \
  --header 'Authorization: Bearer <your-own-wi_live_key>'

Use /mcp to inspect the connection. Official HTTP transport/header documentation. Populate the key privately; shell history and local client settings may retain entered credentials.

Claude.ai / Claude Desktop custom connectors

Settings → Connectors → Add custom connector → endpoint URL. Official remote connector guide. Limitation: some connector UIs support OAuth or no-auth only and do not expose arbitrary bearer headers. This server rejects no-auth and does not implement OAuth, so those UIs cannot connect directly. Availability of a bearer-header field is verify in-app; use Claude Code in the meantime. Do not put the key in the URL.

Develop / self-host

Node 20+.

npm ci
npm test               # mocked fetch, never calls production
npm run build
npm run typecheck:worker
npm start              # Node entry on :3100 (PORT, WARMINBOX_API_BASE env)
npx wrangler deploy    # or deploy src/worker.ts to Cloudflare Workers (wrangler.jsonc)

src/core/ holds the shared API client, tools and server card; src/node.ts (Express) and src/worker.ts (Workers) are thin entrypoints. ecosystem.config.cjs is a PM2 example for running the Node entry behind a reverse proxy.

Listing files

server.json (MCP Registry), .well-known/mcp/server-card.json (snapshot of the live card), glama.json (Glama ownership), .mcp.json / mcp.json / .cursor-plugin/plugin.json (Cursor plugin and cursor.directory).

License

MIT. See LICENSE.