Sendmux Email MCP Server
officialSendmux is an email inbox API and email API for AI agents.
Documentation
MCP
Connect AI tools to Sendmux documentation and product tools.
Sendmux has two MCP connections. Use Documentation MCP when you want an AI tool to search Sendmux docs. Use Product MCP when you want an agent to work with Sendmux tools you authorise.
| Connection | Use it for | Server |
|---|---|---|
| Documentation MCP | Search Sendmux guides and API references. | https://sendmux.ai/docs/mcp |
| Product MCP | Use Management, Mailbox, and Sending tools. | https://mcp.sendmux.ai/mcp or the local sendmux-mcp package |
Documentation MCP
Documentation MCP exposes search_sendmux.
```json theme={null}
{
"mcpServers": {
"sendmux-docs": {
"url": "https://sendmux.ai/docs/mcp"
}
}
}
```
```json theme={null}
{
"servers": {
"sendmux-docs": {
"type": "http",
"url": "https://sendmux.ai/docs/mcp"
}
}
}
```
```toml theme={null}
[mcp_servers.sendmux_docs]
url = "https://sendmux.ai/docs/mcp"
```
Product MCP
Product 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, or an smx_mbx_ key 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, or an smx_mbx_ key locally |
Hosted Product 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.
| Setting | Value |
|---|---|
| Server URL | https://mcp.sendmux.ai/mcp |
| Authorisation server | https://app.sendmux.ai |
| Health check | https://mcp.sendmux.ai/health |
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.
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 a root key. Mailbox and Sending require a mailbox-scoped key.
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` | | 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 \ --mailbox-api-key smx_mbx_... \ --management-api-key smx_root_... \ --sending-api-key smx_mbx_... ```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.