Sendmux CLI

Sendmux CLI

Use this skill when the terminal is the right Sendmux surface.

Boundaries

• Do not ask the user to paste API keys.
• Use smx_root_ keys only for management:* commands.
• Use smx_mbx_ keys or scoped smx_agent_ tokens for mailbox:* commands.
• Durable agent profiles can read and receive mail while active, but cannot send until an invited owner accepts and approves sending.
• After owner approval, sending:* commands with an agent profile automatically exchange and cache a one-hour delegated token.
• Do not run destructive commands without explicit confirmation.
• Use --json for agent-readable output.
• Prefer task-specific Sendmux skills when the user needs strategy; use this skill for exact CLI mechanics.

Install

npm install -g @sendmux/cli
sendmux --help

The package exposes the sendmux binary.

Agent inbox onboarding

No existing Sendmux account or API key is required:

sendmux agent:register my-agent \
  --mailbox-local-part my-agent \
  --client-name "My agent" \
  --default \
  --json

Add --owner-email owner@example.com to invite the owner during registration. Otherwise invite later:

sendmux agent:invite-owner owner@example.com --profile my-agent --json

The CLI persists registration idempotency before the network request, stores the durable credential in the local profile with restricted permissions, never prints it, reloads it from disk, and waits up to 10 minutes for readiness. Rerun registration with the same profile and options to resume safely.

Use the profile for later reads:

sendmux mailbox:messages:list --profile my-agent --query limit=25 --json

Read/receive access has no expiry date while the registration remains active. Sending remains blocked until the owner accepts and approves it. After approval, a command such as sending:send --profile my-agent automatically exchanges the durable credential for a one-hour email.send token and caches it until near expiry. Full registration revocation removes read access and every delegated token.

The inbox is capped at 500 MiB before approval. Enabling owner-approved sending first raises it to at least 5 GiB. Revoking sending does not itself change the current inbox storage allocation.

Profiles

Create separate profiles for root and mailbox keys.

sendmux profiles:set default --api-key "$SENDMUX_ROOT_KEY" --default --json
sendmux profiles:set mailbox --api-key "$SENDMUX_MBX_KEY" --json
sendmux profiles:set sending --api-key "$SENDMUX_MBX_KEY" --json
sendmux profiles:list --json
sendmux profiles:show default --json

Profile reads mask stored API keys and never reveal agent credentials. profiles:set reports key_kind as root or mailbox; agent:register creates a discriminated agent profile.

Authentication resolution:

1. --api-key, then SENDMUX_API_KEY.
2. If no direct key is present, --profile / -p, then SENDMUX_PROFILE, then the configured default profile.
3. Base URL comes from --base-url, then SENDMUX_BASE_URL, then the selected profile.

Preflight

The CLI infers key kind from the prefix before sending a request.

For an agent profile, mailbox:* uses the durable read credential. sending:* obtains a delegated token only after owner approval. management:* rejects agent profiles before the request.

Wrong-key examples fail before network:

Command requires a root API key, but --api-key contains a mailbox API key.
Command requires a send-capable `smx_mbx_` key or owner-approved Sending-resource `smx_agent_` token, but --api-key contains a root API key.

Command catalogue

The CLI exposes generated operation commands:

Use command-level help to discover accepted path, query, header, and body fields:

sendmux management:create-domain --help
sendmux mailbox:search-message-snippets --help
sendmux sending:send:batch --help
sendmux sending:upload-attachment --help

Operation flags

Operation commands share these flags:

--path, --query, and --header require name=value. Booleans use true or false. Repeat an array-valued parameter rather than comma-joining it.

Pass either --body or --body-file, not both.

Use sendmux-attachments for attachment-heavy flows and size/token trade-offs.

Examples

Create a domain:

sendmux management:create-domain \
  --profile default \
  --idempotency-key "$IDEMPOTENCY_KEY" \
  --body '{"domain":"example.com","mode":"send_receive"}' \
  --json

Get domain DNS records:

sendmux management:get-domain-zone-file \
  --profile default \
  --path public_id=mdom_abc \
  --json

Search a mailbox without reading full messages:

sendmux mailbox:search-message-snippets \
  --profile mailbox \
  --query q=invoice \
  --query is_unread=true \
  --query limit=10 \
  --json

Batch-read selected mailbox messages:

sendmux mailbox:batch-get-messages \
  --profile mailbox \
  --body '{
    "ids": ["eml_abc", "eml_def"],
    "body_mode": "clean_json",
    "max_body_chars": 4000
  }' \
  --json

Send a batch:

sendmux sending:send:batch \
  --profile sending \
  --idempotency-key "$IDEMPOTENCY_KEY" \
  --body-file ./messages.json \
  --json

Send through the Sending API with a local attachment:

sendmux sending:send \
  --profile sending \
  --idempotency-key "$IDEMPOTENCY_KEY" \
  --attach ./report.pdf \
  --body '{"from":{"email":"sender@example.com"},"to":{"email":"user@example.com"},"subject":"Report","html_body":"<p>Attached.</p>"}' \
  --json

sending:send --attach uploads the file first and injects an attachment_id reference; it does not place base64 in the send body.

Upload a Sending attachment separately:

sendmux sending:upload-attachment \
  --profile sending \
  --body-file ./report.pdf \
  --query filename=report.pdf \
  --query content_type=application/pdf \
  --json

Send a mailbox message with a local attachment:

sendmux mailbox:send-message \
  --profile mailbox \
  --idempotency-key "$IDEMPOTENCY_KEY" \
  --attach ./report.pdf \
  --body '{"to":[{"email":"user@example.com","name":null}],"subject":"Report","text_body":"Attached."}' \
  --json

Mailbox attachment upload commands share the 7,500,000 byte per-attachment cap. For larger files, split the file or host it externally and send a link.

Upload a mailbox attachment by presigned URL:

sendmux mailbox:upload-attachment \
  --profile mailbox \
  --file ./report.pdf \
  --via-presigned \
  --json

Poll one unchanged-safe delivery log:

sendmux management:get-email-log \
  --profile default \
  --path public_id=dlog_abc \
  --if-none-match "$ETAG" \
  --json

Routing

• First setup/auth check: sendmux-getting-started.
• Sending strategy and body shape: sendmux-send-email.
• Attachment file paths and presigned upload/download: sendmux-attachments.
• Mailbox read, search, sync, triage, or reply: sendmux-mailbox-agent.
• Account-level management strategy: sendmux-management.
• MCP connection setup: sendmux-mcp-setup.
• Cheapest-call doctrine: sendmux-token-efficient-usage.