Email Inbox API + Sending by Sendmux

Email inbox API, inbound mail, and outbound sending MCP servers for AI agents, with inbound email, clean JSON parsing, webhooks, and multi-provider routing through Sendmux.

This package is the Sendmux MCP. Keep it separate from any documentation-search MCP used by docs tooling.

Documentation

Sendmux docs: sendmux.ai/docs
Management API reference: sendmux.ai/docs/api/introduction
Mailbox API reference: sendmux.ai/docs/mailbox-api/introduction
Sending API reference: sendmux.ai/docs/sending-api/introduction
Source repository: Sendmux/sendmux-sdk

Requirements

Python 3.10 or newer.
A send-capable smx_mbx_* key or owner-approved Sending-resource smx_agent_* token for Sending tools.
A mailbox-scoped smx_mbx_* key or scoped smx_agent_* token for Mailbox tools.
A root smx_root_* key for Management tools.

Installation

pip install sendmux-mcp

Usage

Run a single local server with the per-surface commands.

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 a combined local server with sendmux-mcp.

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

Run all three local surfaces when you have both key types.

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 generic sendmux-mcp command also accepts --surface or --surfaces. The wrapper commands select exactly one surface.

Transports

stdio is the default transport for local agent clients.

SENDMUX_API_KEY=smx_mbx_... sendmux-mcp-mailbox --transport stdio

http and streamable-http expose the MCP endpoint over HTTP. HTTP mode defaults to 127.0.0.1:8765/mcp and requires a separate MCP bearer token unless you explicitly opt out.

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 --path /mcp

/health returns a small JSON health response for the selected surfaces.

Hosted Endpoint

The public hosted MCP endpoint is https://mcp.sendmux.ai/mcp.

For hosted clients, use HTTP transport with OAuth. Do not add manual Authorization headers, API keys, custom OAuth endpoints, or custom scopes unless your client explicitly requires them.

Hosted OAuth clients that omit requested scopes during registration or authorization are supported; the server advertises the hosted scope set through discovery and bearer challenges.

The packaged sendmux-mcp-hosted command runs the hosted server runtime. Local and private deployments should use the local commands above unless you are operating a compatible OAuth-backed hosted environment.

Configuration

Setting	Environment	Default
Tool surfaces	`SENDMUX_MCP_SURFACES`	required for `sendmux-mcp`; wrapper commands select one surface
API key fallback	`SENDMUX_API_KEY`	accepted for compatible single-key setups
Mailbox API key	`SENDMUX_MAILBOX_API_KEY`	required when mailbox is selected unless a compatible fallback is provided
Management API key	`SENDMUX_MANAGEMENT_API_KEY`	required when management is selected unless a compatible fallback is provided
Sending API key	`SENDMUX_SENDING_API_KEY`	required when sending is selected unless the fallback key is a send-capable `smx_mbx_` key or owner-approved Sending-resource `smx_agent_` token
App 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 unless opt-out is enabled
Allow unauthenticated HTTP	`SENDMUX_MCP_ALLOW_UNAUTHENTICATED_HTTP`	`false`
Allowed browser origins	`SENDMUX_MCP_ALLOWED_ORIGINS`	no browser origins
Snapshot directory override	`SENDMUX_MCP_OPENAPI_INPUT_DIR` or `OPENAPI_INPUT_DIR`	packaged snapshots
App snapshot override	`SENDMUX_MCP_APP_OPENAPI`	packaged app snapshot
Sending snapshot override	`SENDMUX_MCP_SENDING_OPENAPI`	packaged sending snapshot
Request timeout	`SENDMUX_MCP_TIMEOUT_SECONDS`	`30`
Retry attempts	`SENDMUX_MCP_RETRY_MAX_ATTEMPTS`	`3`

Packaged OpenAPI snapshots are the default so released tool names, schemas, and descriptions stay stable. Path, directory, and URL overrides are available for development, canary, and debugging runs.

Tool Surfaces

Mailbox: 21 tools for granted mailboxes, profile/session discovery, messages, threads, folders, search, counts, and mailbox sends. Requires an smx_mbx_* key or scoped smx_agent_* token. Agent tokens remain limited by server-side scopes; pre-claim self-registered agent tokens do not include email.send.
Management: 20 tools for domains, mailboxes, logs, metrics, spend summary, and webhooks. Requires an smx_root_* key.
Sending: 2 tools for single and batch sends. Requires an smx_mbx_* key or owner-approved Sending-resource smx_agent_* token.

The server rejects keys with the wrong prefix before starting.

Console Scripts

sendmux-mcp
sendmux-mcp-mailbox
sendmux-mcp-management
sendmux-mcp-sending
sendmux-mcp-hosted

Support

Open an issue in Sendmux/sendmux-sdk with the package name, version, command, transport, and request ID from any API error.

Licence

MIT. See the licence file.

Email Inbox API + Sending by Sendmux