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Use the sendmux CLI when you want terminal access to the same Management, Mailbox, and Sending API surfaces exposed by the SDKs.
Sending commands accept a send-capable smx_mbx_ key or owner-approved agent profile. Mailbox commands accept smx_mbx_ keys or durable agent profiles. Management commands require team-scoped smx_root_ keys.

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Install

On Linux, install the CLI from the Snap Store.
On macOS or Linux, you can also install it with Homebrew.
You can also install it from npm.
Download a standalone tarball from GitHub Releases for linux-x64, linux-arm64, darwin-x64, darwin-arm64, or win32-x64. Check the installed command.

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Register an agent inbox

An agent can create an @myagent.mx inbox without an existing Sendmux account or API key. Registration saves the durable read credential in a private local profile and never prints it.
The command waits up to 10 minutes for inbox provisioning. Rerun the same command with the same profile to resume without creating another registration. If you do not know the owner email during registration, invite them later.
The durable profile can read and receive mail without an expiry date unless the complete registration is revoked. After the owner accepts the invitation and approves sending, Sending commands automatically exchange the durable credential for a one-hour email.send token. The self-registered inbox is capped at 500 MiB before approval. Sending approval raises it to at least 5 GiB before the CLI can obtain a delegated sending token. Revoking sending does not itself change the current inbox storage allocation.

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Configure profiles

Save API keys as local CLI profiles so you do not pass a key on every command.
The CLI stores profile configuration locally with restricted file permissions. profiles:list --verbose and profiles:show mask saved keys.

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Authentication order

Every API command resolves credentials in this order:
  1. --api-key
  2. SENDMUX_API_KEY
  3. --profile
  4. SENDMUX_PROFILE
  5. the configured default profile
--base-url overrides the API base URL for one command. SENDMUX_BASE_URL overrides it for the current shell. A profile can also store a base URL override. Before running the API call, the CLI checks that the key or profile matches the command surface. A management command fails early when it receives a mailbox-compatible key, and sending commands fail early when they receive a root key. Mailbox commands accept smx_mbx_ keys and durable smx_agent_ profiles. API permissions still apply, so a durable read token cannot send email before owner acceptance and approval.

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Run commands

Commands use colon-separated names.
Pass request bodies inline with --body or from a file with --body-file.
Pass parameters with repeatable name=value flags:
  • --path name=value for path parameters.
  • --query name=value for query parameters.
  • --header name=value for supported headers.
Typed values are validated before the request is sent. Unknown parameter names fail with the supported names for that command.

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Output

Without --json, API commands print formatted JSON for easy reading. Use --json when another process needs machine-readable output from the CLI.
Text responses return { "text": "..." } with --json. Binary responses return base64 data and byte_length.

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Request safety flags

Use the dedicated safety flags when the generated command supports the corresponding header: The CLI rejects these flags on commands whose API operation does not accept the matching header.

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Command reference

The CLI command set is generated from the public API surfaces. Run sendmux --help to see the current topics, sendmux <topic> --help to browse a surface, and sendmux <command> --help for the flags supported by one command. For example:

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Next steps

SDK overview

Choose package-managed clients for application code.

API keys

Create scoped credentials before configuring CLI profiles.

Mailbox API

Review the API used by mailbox commands.

Management API

Review the API used by management commands.