smails MCP Server

smails

Disposable email for humans and AI agents. An instant, anonymous throwaway inbox for sign-ups, one-time codes, and confirmations — with a REST API, a CLI, and an MCP server, so your AI agent can receive verification emails too. No signup, no password.

→ smails.dev · npx @smails/cli create

Give your agent its own inbox: plug the MCP server into Claude, Cursor, or any MCP client and it can create a mailbox and read incoming mail (verification codes, magic links) on its own.

Features

• Instant inbox — open the site and you have an address, zero clicks
• Real-time — new mail arrives over WebSocket, no polling
• Built for agents — REST API, CLI, and an MCP server share the same mailbox
• Multi-domain — pick from configurable receiving domains
• Self-cleaning — mailboxes auto-expire after 7 days of inactivity
• Serverless — Cloudflare Workers + Durable Objects (one DO per mailbox, SQLite storage)

Quick start

Web

Visit smails.dev — an inbox is created for you on first load.

CLI

npx @smails/cli create      # create a mailbox (token saved to ~/.smails)
npx @smails/cli inbox       # list messages
npx @smails/cli read <id>   # read a message (id prefix is enough)
npx @smails/cli whoami      # show the current address
npx @smails/cli create --force  # replace with a fresh mailbox

MCP (for AI agents)

Add the server to any MCP client (e.g. Claude Desktop, ~/.claude/mcp.json):

{
  "mcpServers": {
    "smails": { "command": "npx", "args": ["@smails/cli", "mcp"] }
  }
}

Tools: create_mailbox, list_messages, read_message, delete_message, get_address.

REST API

# create a mailbox
curl -X POST https://smails.dev/api/mailbox
# → { "address": "...", "token": "..." }

# list messages with the returned token
curl https://smails.dev/api/mailbox/messages \
  -H "Authorization: Bearer <token>"

Authenticate every request (except create) with Authorization: Bearer <token>.

How it works

Inbound mail ──▶ Cloudflare Email Routing (catch-all)
                          │
                          ▼
                  Worker  email() handler ──┐
                                            ▼
   Web / CLI / MCP ──REST + WS──▶  Durable Object  (one per mailbox)
                                   ├─ SQLite (messages)
                                   ├─ token auth
                                   └─ 7-day alarm → cleanup

• Each mailbox is a single Durable Object, addressed by its name; messages live in the DO's SQLite.
• The token is {address}.{secret}; the Worker routes by address, the DO verifies the full token.
• A 7-day alarm wipes inactive mailboxes; any activity renews it.

Project structure

frontend/   React Router SPA (prerendered) — Tailwind v4 + shadcn
worker/     Cloudflare Worker + Durable Objects — Hono routing, postal-mime parsing
cli/        npm package — CLI + MCP server (@smails/cli)

Development

Each package is independent (pnpm). Install per package.

# frontend
cd frontend && pnpm install && pnpm dev

# worker (API + Durable Objects)
cd worker && pnpm install && pnpm dev

# cli / mcp
cd cli && pnpm install && pnpm build
SMAILS_API_URL=http://localhost:8787 node dist/index.js create

Deployment

There are two independent release tracks — pushing to main ships the service, but not the CLI.

Worker + frontend — auto-deployed by Cloudflare Workers Builds on every push to main (the frontend builds to static assets the Worker serves). No manual step. To deploy by hand instead:

cd frontend && pnpm build         # → build/client
cd ../worker && pnpm run deploy   # wrangler deploy — serves assets + API + DOs

CLI (@smails/cli) + MCP server — not auto-deployed; publishing is a separate, manual release:

1. Bump the version in cli/package.json (npm rejects re-publishing an existing version).
2. Push to main.
3. gh release create cli-vX.Y.Z --target main — creating the GitHub Release triggers .github/workflows/publish-cli.yml, which publishes to npm and syncs the MCP registry listing from server.json.

server.json's description must be ≤ 100 characters or the MCP registry publish step 422s.

Receiving mail uses Cloudflare Email Routing (catch-all → the Worker's email handler). Configure receiving domains via the DOMAINS var and the route in worker/wrangler.jsonc.

License

MIT