Sendmux Email MCP

official

Sendmux is an email inbox API and email API for AI agents.

View on sendmux.ai

What can you do with Sendmux Email MCP?

Search Sendmux documentation — Ask your AI assistant to look up Sendmux guides and API references via search_sendmux from the Doc Search MCP connection.
Manage mailboxes — Instruct your assistant to search, read, organize, and send emails from mailboxes you've granted access to through the Mailbox surface.
Oversee team resources — Have your assistant manage domains, mailboxes, sending accounts, logs, metrics, billing, and webhooks using the Management surface.
Send single or batch emails — Direct your assistant to compose and dispatch individual or bulk email messages through the Sending surface.

Documentation

MCP

Connect AI tools to Sendmux documentation and product tools.

Sendmux has two MCP connections. Use Doc Search MCP when you want an AI tool to search Sendmux docs. Use MCP when you want an agent to work with Sendmux tools you authorise.

Connection	Use it for	Server
Doc Search MCP	Search Sendmux guides and API references.	`https://sendmux.ai/docs/mcp`
MCP	Use Management, Mailbox, and Sending tools.	`https://mcp.sendmux.ai/mcp` or the local `sendmux-mcp` package

Info

MCP exposes a curated agent toolset, not every API endpoint. Use the SDKs, CLI, or API reference when you need full endpoint coverage.

Doc Search MCP

Doc Search MCP exposes search_sendmux.

```bash theme={null} claude mcp add sendmux-docs --transport http https://sendmux.ai/docs/mcp ``` Add this server to `.cursor/mcp.json` for one project or `~/.cursor/mcp.json` for all projects.

```json theme={null}
{
  "mcpServers": {
    "sendmux-docs": {
      "url": "https://sendmux.ai/docs/mcp"
    }
  }
}
```

Add this server to your user or workspace `mcp.json`.

```json theme={null}
{
  "servers": {
    "sendmux-docs": {
      "type": "http",
      "url": "https://sendmux.ai/docs/mcp"
    }
  }
}
```

Add this server to `~/.codex/config.toml` or a trusted project `.codex/config.toml`.

```toml theme={null}
[mcp_servers.sendmux_docs]
url = "https://sendmux.ai/docs/mcp"
```

MCP

MCP exposes the product surfaces you grant.

Surface	Use it for	Access
Mailbox	Search, read, organise, and send from granted mailboxes.	Hosted grant with Mailbox access, an `smx_mbx_` key, or a scoped `smx_agent_` token locally
Management	Manage team resources such as domains, mailboxes, sending accounts, logs, metrics, billing, and webhooks.	Hosted grant with Management access, or an `smx_root_` key locally
Sending	Send single or batch emails.	Hosted grant with Sending access, an `smx_mbx_` key, or an owner-approved Sending-resource `smx_agent_` token locally

Hosted MCP is the default when your client supports remote MCP with browser OAuth. It keeps Sendmux in the authorisation flow, avoids distributing manual API keys to agents, and shows only the tools allowed by the grant.

Info

Package identity: sendmux-mcp

Package version: 2.1.2

Hosted resource: https://mcp.sendmux.ai/mcp

Hosted transport: Streamable HTTP

Curated tool count: 54

Certified protocol versions: 2025-11-25, 2026-07-28

Runtime-accepted protocol versions: 2024-11-05, 2025-03-26, 2025-06-18, 2025-11-25, 2026-07-28. Runtime acceptance provides compatibility; it does not certify each version.

Setting	Value
Server URL	`https://mcp.sendmux.ai/mcp`
Authorisation server	`https://app.sendmux.ai`
Health check	`https://mcp.sendmux.ai/health`

Use the Postman collection when you want to test MCP requests from Postman:

When you connect, Sendmux asks you to choose a team, product surfaces, and mailbox access where relevant. Access tokens are short-lived. Refresh tokens rotate on use and can last up to 30 days unless the connection is disconnected or expires.

Note

If you grant more than one mailbox, start mailbox workflows with mailbox_list_granted_mailboxes and pass the returned mailbox_id to tools that act on one mailbox.

Connection modes

Use when your client can open a browser-based MCP OAuth flow. Use when your coding agent can launch a local command on your machine. Use when a client needs a URL but you run the MCP package yourself.

Local package

Install the local package from PyPI:

pip install sendmux-mcp

Run one surface:

SENDMUX_API_KEY=smx_mbx_... sendmux-mcp-mailbox
SENDMUX_API_KEY=smx_root_... sendmux-mcp-management
SENDMUX_API_KEY=smx_mbx_... sendmux-mcp-sending

Run all product surfaces:

SENDMUX_MCP_SURFACES=mailbox,management,sending \
SENDMUX_MAILBOX_API_KEY=smx_mbx_... \
SENDMUX_MANAGEMENT_API_KEY=smx_root_... \
SENDMUX_SENDING_API_KEY=smx_mbx_... \
sendmux-mcp

The server validates key prefixes before starting. Management requires smx_root_. Sending accepts a send-capable smx_mbx_ key or owner-approved Sending-resource smx_agent_ token. Mailbox accepts an smx_mbx_ key or a scoped smx_agent_ token.

Private HTTP

HTTP mode is useful when your MCP client connects to a server URL but you still want to run the package yourself.

SENDMUX_API_KEY=smx_mbx_... \
SENDMUX_MCP_HTTP_BEARER_TOKEN=local-mcp-token \
sendmux-mcp-mailbox --transport http --host 127.0.0.1 --port 8765

The endpoint defaults to /mcp. /health returns the selected surfaces. HTTP mode requires SENDMUX_MCP_HTTP_BEARER_TOKEN unless you explicitly start it with --allow-unauthenticated-http.

Configuration reference

| Setting | Environment | Default | | ----------------------------------- | --------------------------------------- | -------------------------------- | | Tool surfaces | `SENDMUX_MCP_SURFACES` | Required for `sendmux-mcp` | | API key fallback | `SENDMUX_API_KEY` | None | | Mailbox API key | `SENDMUX_MAILBOX_API_KEY` | None | | Management API key | `SENDMUX_MANAGEMENT_API_KEY` | None | | Sending API key | `SENDMUX_SENDING_API_KEY` | None | | Management and Mailbox API base URL | `SENDMUX_APP_BASE_URL` | `https://app.sendmux.ai/api/v1` | | Sending API base URL | `SENDMUX_SENDING_BASE_URL` | `https://smtp.sendmux.ai/api/v1` | | Retry time budget, in seconds | `SENDMUX_MCP_RETRY_MAX_ELAPSED_SECONDS` | Unset | | Transport | `SENDMUX_MCP_TRANSPORT` | `stdio` | | HTTP host | `SENDMUX_MCP_HOST` | `127.0.0.1` | | HTTP port | `SENDMUX_MCP_PORT` | `8765` | | HTTP path | `SENDMUX_MCP_PATH` | `/mcp` | | HTTP bearer token | `SENDMUX_MCP_HTTP_BEARER_TOKEN` | Required for HTTP | | Allowed browser origins | `SENDMUX_MCP_ALLOWED_ORIGINS` | No browser origins | ```bash theme={null} SENDMUX_MCP_SURFACES=mailbox,management,sending \ SENDMUX_MAILBOX_API_KEY="$SENDMUX_MAILBOX_KEY" \ SENDMUX_MANAGEMENT_API_KEY="$SENDMUX_ROOT_KEY" \ SENDMUX_SENDING_API_KEY="$SENDMUX_SENDING_KEY" \ sendmux-mcp ```

Tool discovery

Tool names are generated from the current public API surfaces. Open your MCP client's tool picker after authorisation to see the tools available to that connection.

Hosted connections show only the tools allowed by the selected product surfaces, permissions, and mailbox grant. Local servers show the tools for the surfaces and keys you provide at startup.

Troubleshooting

Confirm the selected product surfaces and granted permissions. Hosted connections show only tools allowed by the grant. Check the API key prefix. Management needs `smx_root_`; Sending accepts `smx_mbx_` or owner-approved Sending-resource `smx_agent_`; Mailbox accepts `smx_mbx_` or scoped `smx_agent_`. Send `Authorization: Bearer ` to private HTTP, or complete OAuth for hosted MCP. Add the browser client's origin to `SENDMUX_MCP_ALLOWED_ORIGINS` for private HTTP. Connect only the surfaces you need, or disable unused tools in the client.

Next steps

Use Sendmux through an A2A 1.0 agent endpoint with hosted OAuth. Configure Sendmux MCP in Claude Code, Cursor, Codex, Gemini CLI, Qwen Code, Zed, and more. Use package-managed clients from application code. Install the CLI with Snap, Homebrew, or npm when you need terminal access. Create scoped credentials for local MCP setups.