Hello.
\",\n \"text_body\": \"Hello.\"\n}\n```\n\nRequired fields: `from`, `to`, `subject`, `html_body`.\n\nUseful optional fields:\n\n- `text_body`: plain text alternative.\n- `cc`, `bcc`: arrays of recipients, max 49 each and subject to 50 total `to`, `cc`, and `bcc` recipients.\n- `reply_to`: one address object.\n- `return_path`: envelope sender for bounce handling.\n- `custom_headers`: custom `X-*` headers.\n- `attachments`: up to 10 items. Prefer uploaded refs `{ \"attachment_id\": \"att_...\" }`. Inline compatibility form uses `filename` plus base64 `content`, optional `type`, and `encoding: \"base64\"`.\n\nFor real local files, do not ask the model to produce base64. Route attachment-heavy work to `sendmux-attachments`; use CLI `--attach`, SDK file helpers, or delegated `sending_create_attachment_upload`, then pass `attachment_id` refs. For a presigned Sending upload, the upload intent's returned `max_size_bytes` is the size authority; the final sent message is capped at 25 MB. Mailbox `blob_id` refs are for mailbox sends, not Sending API sends.\n\nFor a direct HTTP batch call, keep authority and retry metadata outside the JSON body:\n\n```http\nPOST /emails/send/batch HTTP/1.1\nAuthorization: Bearer $SENDMUX_MBX_KEY\nContent-Type: application/json\nIdempotency-Key: $IDEMPOTENCY_KEY\n```\n\n`$SENDMUX_MBX_KEY` must resolve to a send-capable `smx_mbx_` key. An owner-approved Sending-resource `smx_agent_` token is also accepted. The request body is:\n\n```json\n{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Tiny agent-authored content: `sending_upload_attachment` with `content_base64` only when the decoded content is at most 32,768 bytes.\n- Real local file upload before send: complete every step below.\n 1. Call `sending_create_attachment_upload` with the filename, content type, and exact local `size_bytes`; compare the size with returned `max_size_bytes`.\n 2. Transfer bytes outside model context using the exact returned method, URL, and headers with no Sendmux API key. Keep the signed URL and returned headers out of process arguments and retained output.\n 3. Take `attachment_id` from the successful external upload response. The intent returns `upload_id` and transfer metadata, not `attachment_id`; never substitute its `upload_id` or a Mailbox `blob_id`.\n 4. Pass that `attachment_id` to `sending_send_email` with one stable `Idempotency-Key` for this logical send when the client exposes it. If MCP does not expose it clearly, use CLI, SDK, or direct HTTP for a retry-sensitive send.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nFor attachments through MCP, use `sendmux-attachments` so the agent chooses presigned upload or tiny inline base64 correctly; MCP does not receive a local `file_path`.\n\n## CLI\n\nFor a self-registered agent, use its profile instead of copying credentials:\n\n```bash\nsendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json\n```\n\nThe owner must already have accepted the invitation and approved sending. The CLI obtains and caches the short-lived delegated token; the durable read credential is not used directly by the Sending API.\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n throwOnError: true,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.data.message_id, response.data.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n throwOnError: true,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl --silent --show-error --fail-with-body \\\n --config - \\\n --data-binary @sendmux-email.json <Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Tiny agent-authored content: `sending_upload_attachment` with `content_base64` only when the decoded content is at most 32,768 bytes.\n- Real local file upload before send: complete every step below.\n 1. Call `sending_create_attachment_upload` with the filename, content type, and exact local `size_bytes`; compare the size with returned `max_size_bytes`.\n 2. Transfer bytes outside model context using the exact returned method, URL, and headers with no Sendmux API key. Keep the signed URL and returned headers out of process arguments and retained output.\n 3. Take `attachment_id` from the successful external upload response. The intent returns `upload_id` and transfer metadata, not `attachment_id`; never substitute its `upload_id` or a Mailbox `blob_id`.\n 4. Pass that `attachment_id` to `sending_send_email` with one stable `Idempotency-Key` for this logical send when the client exposes it. If MCP does not expose it clearly, use CLI, SDK, or direct HTTP for a retry-sensitive send.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nFor attachments through MCP, use `sendmux-attachments` so the agent chooses presigned upload or tiny inline base64 correctly; MCP does not receive a local `file_path`.\n\n## CLI\n\nFor a self-registered agent, use its profile instead of copying credentials:\n\n```bash\nsendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json\n```\n\nThe owner must already have accepted the invitation and approved sending. The CLI obtains and caches the short-lived delegated token; the durable read credential is not used directly by the Sending API.\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n throwOnError: true,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.data.message_id, response.data.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n throwOnError: true,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl --silent --show-error --fail-with-body \\\n --config - \\\n --data-binary @sendmux-email.json <Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Tiny agent-authored content: `sending_upload_attachment` with `content_base64` only when the decoded content is at most 32,768 bytes.\n- Real local file upload before send: complete every step below.\n 1. Call `sending_create_attachment_upload` with the filename, content type, and exact local `size_bytes`; compare the size with returned `max_size_bytes`.\n 2. Transfer bytes outside model context using the exact returned method, URL, and headers with no Sendmux API key. Keep the signed URL and returned headers out of process arguments and retained output.\n 3. Take `attachment_id` from the successful external upload response. The intent returns `upload_id` and transfer metadata, not `attachment_id`; never substitute its `upload_id` or a Mailbox `blob_id`.\n 4. Pass that `attachment_id` to `sending_send_email` with one stable `Idempotency-Key` for this logical send when the client exposes it. If MCP does not expose it clearly, use CLI, SDK, or direct HTTP for a retry-sensitive send.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nFor attachments through MCP, use `sendmux-attachments` so the agent chooses presigned upload or tiny inline base64 correctly; MCP does not receive a local `file_path`.\n\n## CLI\n\nFor a self-registered agent, use its profile instead of copying credentials:\n\n```bash\nsendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json\n```\n\nThe owner must already have accepted the invitation and approved sending. The CLI obtains and caches the short-lived delegated token; the durable read credential is not used directly by the Sending API.\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n throwOnError: true,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.data.message_id, response.data.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n throwOnError: true,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl --silent --show-error --fail-with-body \\\n --config - \\\n --data-binary @sendmux-email.json <Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Local file upload before send: `sending_upload_attachment` with `file_path`.\n- Hosted or shell-capable upload before send: `sending_create_attachment_upload`, then `PUT` bytes to the returned URL with the returned headers and no Sendmux API key.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nInclude an idempotency key when the client exposes the header parameter. If the MCP client does not expose headers clearly, use CLI, SDK, or direct HTTP for retry-sensitive sends. For attachments through MCP, use `sendmux-attachments` so the agent chooses `file_path`, presigned upload, or tiny inline base64 correctly.\n\n## CLI\n\nFor a self-registered agent, use its profile instead of copying credentials:\n\n```bash\nsendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json\n```\n\nThe owner must already have accepted the invitation and approved sending. The CLI obtains and caches the short-lived delegated token; the durable read credential is not used directly by the Sending API.\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.message_id, response.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl -X POST https://smtp.sendmux.ai/api/v1/emails/send \\\n -H \"Authorization: Bearer $SENDMUX_MBX_KEY\" \\\n -H \"Content-Type: application/json\" \\\n -H \"Idempotency-Key: $IDEMPOTENCY_KEY\" \\\n -d @sendmux-email.json\n```\n\n## Responses and errors\n\nSingle send success returns a `200` success envelope with:\n\n- `data.message_id`: `eml_...`\n- `data.status`: `queued`\n\nBatch success returns a `200` success envelope with:\n\n- `data.summary.total`\n- `data.summary.queued`\n- `data.summary.failed`\n- `data.results[]` containing `index`, `status`, `message_id`, and optional `error`\n\nHandle these errors deliberately:\n\n- `401`: missing, invalid, or revoked key.\n- `402`: insufficient credits.\n- `403`: key lacks `email.send`, is not allowed for the sender, or uses the wrong surface.\n- `409`: idempotency conflict.\n- `413`: request body exceeds 25 MB.\n- `422`: validation failed; read `error.errors`.\n- `429` or `503`: retry according to response headers.\n\n## Routing\n\n- Setup/auth first call: `sendmux-getting-started`.\n- Attachment file paths, presigned upload URLs, and download URLs: `sendmux-attachments`.\n- Mailbox-centred replies: `sendmux-mailbox-agent`.\n- CLI-only details: `sendmux-cli`.\n- Cheapest-call decisions: `sendmux-token-efficient-usage`.\n\nFile v1.0.8:_meta.json\n\n{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.8\",\n \"publishedAt\": 1789099223727\n}\n\nFile v1.0.8:skill-card.md\n\n## Description:\n\nSend one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\n\nThis skill is ready for commercial/non-commercial use.\n\n## Publisher:\n\n[sendmux.ai](https://clawhub.ai/user/sendmux.ai)\n\n### License/Terms of Use:\n\nMIT-0\n\n## Use Case:\n\nExternal developers and agents use this skill to prepare or execute Sendmux outbound email workflows through MCP, CLI, SDKs, or direct HTTP. It supports single and batch sends, attachment handling, idempotency, and credential-safe send-path selection.\n\n### Deployment Geography for Use:\n\nGlobal\n\n## Known Risks and Mitigations:\n\nRisk: Agents may send email to external recipients with unintended recipients, content, or attachments.\n\nMitigation: Require user confirmation of every recipient, message body, and attachment before sending.\n\nRisk: Credentials with broad or incorrect send permissions could expose mail-sending capability beyond the intended workflow.\n\nMitigation: Use scoped send-capable credentials or delegated tokens and avoid asking users to paste secrets into chat.\n\nRisk: Retries can duplicate outbound email or conflict with a changed message body.\n\nMitigation: Use one stable idempotency key per logical email or batch and handle idempotency conflicts deliberately.\n\n## Reference(s):\n\n- [Sendmux skills repository](https://github.com/Sendmux/skills)\n- [Sendmux Sending API endpoint](https://smtp.sendmux.ai/api/v1/emails/send)\n- [ClawHub skill page](https://clawhub.ai/sendmux.ai/skills/sendmux-send-email)\n\n## Skill Output:\n\n**Output Type(s):** [guidance, markdown, code, shell commands, configuration]\n\n**Output Format:** [Markdown with JSON, TypeScript, and bash examples]\n\n**Output Parameters:** [1D]\n\n**Other Properties Related to Output:** [May include Sendmux API request bodies, MCP tool choices, CLI commands, SDK snippets, and retry/error-handling guidance.]\n\n## Skill Version(s):\n\n1.0.8 (source: server release evidence)\n\n## Ethical Considerations:\n\nUsers should evaluate whether this skill is appropriate for their environment, review any generated or modified files before relying on them, and apply their organization's safety, security, and compliance requirements before deployment.\n\nArchive v1.0.7: 3 files, 5136 bytes\n\nFiles: skill-card.md (2235b), SKILL.md (9692b), _meta.json (137b)\n\nFile v1.0.7:SKILL.md\n\n---\nname: \"sendmux-send-email\"\ndescription: \"Send one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\"\nversion: \"1.4.2\"\nmetadata:\n openclaw:\n skillKey: \"sendmux-send-email\"\n homepage: \"https://github.com/Sendmux/skills\"\n primaryEnv: \"SENDMUX_API_KEY\"\n envVars:\n - name: \"SENDMUX_API_KEY\"\n required: false\n description: \"Optional Sendmux API key or scoped agent token used by CLI, SDK, HTTP, or MCP examples.\"\n - name: \"SENDMUX_MBX_KEY\"\n required: false\n description: \"Optional Sendmux mailbox key for Mailbox and send-capable mailbox workflows.\"\n---\n\n# Sendmux send email\n\n## ClawHub account note\n\nThis ClawHub skill connects OpenClaw agents to Sendmux. Some workflows require a Sendmux account and an appropriate Sendmux API key or agent token. Sendmux account usage is external to ClawHub; do not ask users to paste secrets into chat.\n\nUse this skill when the user is ready to send outbound email through Sendmux or needs code/commands for sending.\n\n## Safety first\n\n- Do not ask the user to paste an API key.\n- Do not invent recipients, sender addresses, subject lines, or body content.\n- Send only after the user supplies or confirms every recipient and message.\n- For batch sends, confirm the full recipient/message set before calling a send tool.\n- Use a send-capable `smx_mbx_` key or owner-approved Sending-resource `smx_agent_` token for the Sending API.\n- A durable agent profile is read/receive-only. Do not treat its stored credential as send-capable.\n- Before owner acceptance and sending approval, agent-profile sends fail closed. After approval, the CLI exchanges and caches a one-hour delegated `email.send` token automatically.\n- The self-registered inbox is capped at 500 MiB before approval. Sending approval raises it to at least 5 GiB first. Revoking sending does not itself change the current inbox storage allocation.\n\n## Choose the send path\n\n| User task | Efficient default |\n| ----------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |\n| One outbound email | `POST /emails/send`, MCP `sending_send_email`, CLI `sending:send`, or SDK `sendingSendEmail`. |\n| More than one independent outbound email | Batch by default: `POST /emails/send/batch`, MCP `sending_send_email_batch`, CLI `sending:send:batch`, or SDK `sendingSendEmailBatch`. |\n| Sending API attachment file | Upload first with `sending_upload_attachment`, `sending_create_attachment_upload`, CLI `--attach`, or SDK file helpers; send by `attachment_id`. |\n| Replying while working inside one mailbox | Use mailbox send from `sendmux-mailbox-agent` when the workflow is mailbox-centred. |\n| Existing app only supports SMTP | Use SMTP only because the existing tool requires it. For new agent or app integrations, prefer the HTTP Sending API. |\n\nBatch sends accept up to 100 messages. A batch response can partially succeed, so inspect every result item.\n\n## Required JSON shape\n\nSingle send body:\n\n```json\n{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n}\n```\n\nRequired fields: `from`, `to`, `subject`, `html_body`.\n\nUseful optional fields:\n\n- `text_body`: plain text alternative.\n- `cc`, `bcc`: arrays of recipients, max 100 each.\n- `reply_to`: one address object.\n- `return_path`: envelope sender for bounce handling.\n- `custom_headers`: custom `X-*` headers.\n- `attachments`: up to 10 items. Prefer uploaded refs `{ \"attachment_id\": \"att_...\" }`. Inline compatibility form uses `filename` plus base64 `content`, optional `type`, and `encoding: \"base64\"`.\n\nFor real local files, do not ask the model to produce base64. Route attachment-heavy work to `sendmux-attachments`; use CLI `--attach`, SDK file helpers, `sending_upload_attachment`, or delegated `sending_create_attachment_upload`, then pass `attachment_id` refs. Sending uploads cap each file at 18 MiB and the final sent message at 25 MB. Mailbox `blob_id` refs are for mailbox sends, not Sending API sends.\n\nBatch send body:\n\n```json\n{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Local file upload before send: `sending_upload_attachment` with `file_path`.\n- Hosted or shell-capable upload before send: `sending_create_attachment_upload`, then `PUT` bytes to the returned URL with the returned headers and no Sendmux API key.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nInclude an idempotency key when the client exposes the header parameter. If the MCP client does not expose headers clearly, use CLI, SDK, or direct HTTP for retry-sensitive sends. For attachments through MCP, use `sendmux-attachments` so the agent chooses `file_path`, presigned upload, or tiny inline base64 correctly.\n\n## CLI\n\nFor a self-registered agent, use its profile instead of copying credentials:\n\n```bash\nsendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json\n```\n\nThe owner must already have accepted the invitation and approved sending. The CLI obtains and caches the short-lived delegated token; the durable read credential is not used directly by the Sending API.\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.message_id, response.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl -X POST https://smtp.sendmux.ai/api/v1/emails/send \\\n -H \"Authorization: Bearer $SENDMUX_MBX_KEY\" \\\n -H \"Content-Type: application/json\" \\\n -H \"Idempotency-Key: $IDEMPOTENCY_KEY\" \\\n -d @sendmux-email.json\n```\n\n## Responses and errors\n\nSingle send success returns a `200` success envelope with:\n\n- `data.message_id`: `eml_...`\n- `data.status`: `queued`\n\nBatch success returns a `200` success envelope with:\n\n- `data.summary.total`\n- `data.summary.queued`\n- `data.summary.failed`\n- `data.results[]` containing `index`, `status`, `message_id`, and optional `error`\n\nHandle these errors deliberately:\n\n- `401`: missing, invalid, or revoked key.\n- `402`: insufficient credits.\n- `403`: key lacks `email.send`, is not allowed for the sender, or uses the wrong surface.\n- `409`: idempotency conflict.\n- `413`: request body exceeds 25 MB.\n- `422`: validation failed; read `error.errors`.\n- `429` or `503`: retry according to response headers.\n\n## Routing\n\n- Setup/auth first call: `sendmux-getting-started`.\n- Attachment file paths, presigned upload URLs, and download URLs: `sendmux-attachments`.\n- Mailbox-centred replies: `sendmux-mailbox-agent`.\n- CLI-only details: `sendmux-cli`.\n- Cheapest-call decisions: `sendmux-token-efficient-usage`.\n\nFile v1.0.7:_meta.json\n\n{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.7\",\n \"publishedAt\": 1788259062785\n}\n\nFile v1.0.7:skill-card.md\n\n## Description:\n\nSend one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\n\nThis skill is ready for commercial/non-commercial use.\n\n## Publisher:\n\n[sendmux.ai](https://clawhub.ai/user/sendmux.ai)\n\n### License/Terms of Use:\n\nMIT-0\n\n## Use Case:\n\nDevelopers and external agent users use this skill when an agent needs to prepare Sendmux email-sending commands, API calls, SDK code, or MCP tool usage with confirmed recipients, message content, credentials, idempotency, and attachments.\n\n### Deployment Geography for Use:\n\nGlobal\n\n## Known Risks and Mitigations:\n\nRisk: An agent could send email to unconfirmed recipients or with unapproved message content.\n\nMitigation: Require review of every recipient, sender, subject, body, batch list, and attachment before allowing a send.\n\nRisk: Sendmux credentials could be exposed if a user pastes secrets into chat.\n\nMitigation: Use scoped or revocable Sendmux credentials and do not ask users to paste API keys into chat.\n\nRisk: Repeated attempts could duplicate sends or trigger idempotency conflicts.\n\nMitigation: Use one stable Idempotency-Key per logical email or batch and handle idempotency conflicts deliberately.\n\n## Reference(s):\n\n- [Sendmux skills homepage](https://github.com/Sendmux/skills)\n- [Sendmux Sending API endpoint](https://smtp.sendmux.ai/api/v1/emails/send)\n- [ClawHub skill page](https://clawhub.ai/sendmux.ai/skills/sendmux-send-email)\n\n## Skill Output:\n\n**Output Type(s):** [Guidance, Markdown, Code, Shell commands, Configuration]\n\n**Output Format:** [Markdown with JSON, TypeScript, and bash examples]\n\n**Output Parameters:** [1D]\n\n**Other Properties Related to Output:** [May include Sendmux API request bodies, CLI commands, SDK snippets, MCP tool choices, idempotency guidance, and attachment-handling guidance.]\n\n## Skill Version(s):\n\n1.0.7 (source: server release metadata); SKILL.md frontmatter reports 1.4.2\n\n## Ethical Considerations:\n\nUsers should evaluate whether this skill is appropriate for their environment, review any generated or modified files before relying on them, and apply their organization's safety, security, and compliance requirements before deployment.\n\nArchive v1.0.6: 3 files, 5128 bytes\n\nFiles: skill-card.md (2310b), SKILL.md (9667b), _meta.json (137b)\n\nFile v1.0.6:SKILL.md\n\n---\nname: \"sendmux-send-email\"\ndescription: \"Send one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\"\nversion: \"1.4.1\"\nmetadata:\n openclaw:\n skillKey: \"sendmux-send-email\"\n homepage: \"https://github.com/Sendmux/skills\"\n primaryEnv: \"SENDMUX_API_KEY\"\n envVars:\n - name: \"SENDMUX_API_KEY\"\n required: false\n description: \"Optional Sendmux API key or scoped agent token used by CLI, SDK, HTTP, or MCP examples.\"\n - name: \"SENDMUX_MBX_KEY\"\n required: false\n description: \"Optional Sendmux mailbox key for Mailbox and send-capable mailbox workflows.\"\n---\n\n# Sendmux send email\n\n## ClawHub account note\n\nThis ClawHub skill connects OpenClaw agents to Sendmux. Some workflows require a Sendmux account and an appropriate Sendmux API key or agent token. Sendmux account usage is external to ClawHub; do not ask users to paste secrets into chat.\n\nUse this skill when the user is ready to send outbound email through Sendmux or needs code/commands for sending.\n\n## Safety first\n\n- Do not ask the user to paste an API key.\n- Do not invent recipients, sender addresses, subject lines, or body content.\n- Send only after the user supplies or confirms every recipient and message.\n- For batch sends, confirm the full recipient/message set before calling a send tool.\n- Use a send-capable `smx_mbx_` key or owner-approved Sending-resource `smx_agent_` token for the Sending API.\n- A durable agent profile is read/receive-only. Do not treat its stored credential as send-capable.\n- Before owner acceptance and sending approval, agent-profile sends fail closed. After approval, the CLI exchanges and caches a one-hour delegated `email.send` token automatically.\n- The self-registered inbox is capped at 500 MiB before approval. Sending approval raises it to at least 5 GiB first; revoking delegated sending later does not shrink it.\n\n## Choose the send path\n\n| User task | Efficient default |\n| ----------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |\n| One outbound email | `POST /emails/send`, MCP `sending_send_email`, CLI `sending:send`, or SDK `sendingSendEmail`. |\n| More than one independent outbound email | Batch by default: `POST /emails/send/batch`, MCP `sending_send_email_batch`, CLI `sending:send:batch`, or SDK `sendingSendEmailBatch`. |\n| Sending API attachment file | Upload first with `sending_upload_attachment`, `sending_create_attachment_upload`, CLI `--attach`, or SDK file helpers; send by `attachment_id`. |\n| Replying while working inside one mailbox | Use mailbox send from `sendmux-mailbox-agent` when the workflow is mailbox-centred. |\n| Existing app only supports SMTP | Use SMTP only because the existing tool requires it. For new agent or app integrations, prefer the HTTP Sending API. |\n\nBatch sends accept up to 100 messages. A batch response can partially succeed, so inspect every result item.\n\n## Required JSON shape\n\nSingle send body:\n\n```json\n{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n}\n```\n\nRequired fields: `from`, `to`, `subject`, `html_body`.\n\nUseful optional fields:\n\n- `text_body`: plain text alternative.\n- `cc`, `bcc`: arrays of recipients, max 100 each.\n- `reply_to`: one address object.\n- `return_path`: envelope sender for bounce handling.\n- `custom_headers`: custom `X-*` headers.\n- `attachments`: up to 10 items. Prefer uploaded refs `{ \"attachment_id\": \"att_...\" }`. Inline compatibility form uses `filename` plus base64 `content`, optional `type`, and `encoding: \"base64\"`.\n\nFor real local files, do not ask the model to produce base64. Route attachment-heavy work to `sendmux-attachments`; use CLI `--attach`, SDK file helpers, `sending_upload_attachment`, or delegated `sending_create_attachment_upload`, then pass `attachment_id` refs. Sending uploads cap each file at 18 MiB and the final sent message at 25 MB. Mailbox `blob_id` refs are for mailbox sends, not Sending API sends.\n\nBatch send body:\n\n```json\n{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Local file upload before send: `sending_upload_attachment` with `file_path`.\n- Hosted or shell-capable upload before send: `sending_create_attachment_upload`, then `PUT` bytes to the returned URL with the returned headers and no Sendmux API key.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nInclude an idempotency key when the client exposes the header parameter. If the MCP client does not expose headers clearly, use CLI, SDK, or direct HTTP for retry-sensitive sends. For attachments through MCP, use `sendmux-attachments` so the agent chooses `file_path`, presigned upload, or tiny inline base64 correctly.\n\n## CLI\n\nFor a self-registered agent, use its profile instead of copying credentials:\n\n```bash\nsendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json\n```\n\nThe owner must already have accepted the invitation and approved sending. The CLI obtains and caches the short-lived delegated token; the durable read credential is not used directly by the Sending API.\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.message_id, response.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl -X POST https://smtp.sendmux.ai/api/v1/emails/send \\\n -H \"Authorization: Bearer $SENDMUX_MBX_KEY\" \\\n -H \"Content-Type: application/json\" \\\n -H \"Idempotency-Key: $IDEMPOTENCY_KEY\" \\\n -d @sendmux-email.json\n```\n\n## Responses and errors\n\nSingle send success returns a `200` success envelope with:\n\n- `data.message_id`: `eml_...`\n- `data.status`: `queued`\n\nBatch success returns a `200` success envelope with:\n\n- `data.summary.total`\n- `data.summary.queued`\n- `data.summary.failed`\n- `data.results[]` containing `index`, `status`, `message_id`, and optional `error`\n\nHandle these errors deliberately:\n\n- `401`: missing, invalid, or revoked key.\n- `402`: insufficient credits.\n- `403`: key lacks `email.send`, is not allowed for the sender, or uses the wrong surface.\n- `409`: idempotency conflict.\n- `413`: request body exceeds 25 MB.\n- `422`: validation failed; read `error.errors`.\n- `429` or `503`: retry according to response headers.\n\n## Routing\n\n- Setup/auth first call: `sendmux-getting-started`.\n- Attachment file paths, presigned upload URLs, and download URLs: `sendmux-attachments`.\n- Mailbox-centred replies: `sendmux-mailbox-agent`.\n- CLI-only details: `sendmux-cli`.\n- Cheapest-call decisions: `sendmux-token-efficient-usage`.\n\nFile v1.0.6:_meta.json\n\n{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.6\",\n \"publishedAt\": 1788258524673\n}\n\nFile v1.0.6:skill-card.md\n\n## Description:\n\nSend one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\n\nThis skill is ready for commercial/non-commercial use.\n\n## Publisher:\n\n[sendmux.ai](https://clawhub.ai/user/sendmux.ai)\n\n### License/Terms of Use:\n\nMIT-0\n\n## Use Case:\n\nExternal developers and agents use this skill to prepare and send outbound Sendmux email through MCP, CLI, SDK, or HTTP workflows after the user confirms recipients and message content.\n\n### Deployment Geography for Use:\n\nGlobal\n\n## Known Risks and Mitigations:\n\nRisk: An agent could send email to unintended recipients or with unintended content.\n\nMitigation: Confirm every recipient, subject, body, and batch item with the user before invoking any send-capable workflow.\n\nRisk: Sendmux credentials could be exposed if copied into chat or stored in prompts.\n\nMitigation: Use environment variables or approved credential profiles, and do not ask users to paste API keys into chat.\n\nRisk: Retrying sends without idempotency controls can create duplicate sends or idempotency conflicts.\n\nMitigation: Use a stable idempotency key for each retryable email or batch and inspect conflict responses before retrying.\n\nRisk: Attachments can exceed supported upload or message-size limits.\n\nMitigation: Use Sendmux attachment upload workflows and respect the documented per-file and final message limits before sending.\n\n## Reference(s):\n\n- [Sendmux skills repository](https://github.com/Sendmux/skills)\n\n## Skill Output:\n\n**Output Type(s):** [guidance, markdown, code, shell commands, configuration]\n\n**Output Format:** [Markdown guidance with JSON payloads, TypeScript examples, shell commands, and HTTP examples.]\n\n**Output Parameters:** [1D]\n\n**Other Properties Related to Output:** [May include send payloads, idempotency keys, API calls, attachment references, and credential environment variable names; does not require users to paste secrets into chat.]\n\n## Skill Version(s):\n\n1.0.6 (source: server release evidence)\n\n## Ethical Considerations:\n\nUsers should evaluate whether this skill is appropriate for their environment, review any generated or modified files before relying on them, and apply their organization's safety, security, and compliance requirements before deployment.\n\nArchive v1.0.5: 3 files, 5150 bytes\n\nFiles: skill-card.md (2338b), SKILL.md (9658b), _meta.json (137b)\n\nFile v1.0.5:SKILL.md\n\n---\nname: \"sendmux-send-email\"\ndescription: \"Send one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\"\nversion: \"1.4.0\"\nmetadata:\n openclaw:\n skillKey: \"sendmux-send-email\"\n homepage: \"https://github.com/Sendmux/skills\"\n primaryEnv: \"SENDMUX_API_KEY\"\n envVars:\n - name: \"SENDMUX_API_KEY\"\n required: false\n description: \"Optional Sendmux API key or scoped agent token used by CLI, SDK, HTTP, or MCP examples.\"\n - name: \"SENDMUX_MBX_KEY\"\n required: false\n description: \"Optional Sendmux mailbox key for Mailbox and send-capable mailbox workflows.\"\n---\n\n# Sendmux send email\n\n## ClawHub account note\n\nThis ClawHub skill connects OpenClaw agents to Sendmux. Some workflows require a Sendmux account and an appropriate Sendmux API key or agent token. Sendmux account usage is external to ClawHub; do not ask users to paste secrets into chat.\n\nUse this skill when the user is ready to send outbound email through Sendmux or needs code/commands for sending.\n\n## Safety first\n\n- Do not ask the user to paste an API key.\n- Do not invent recipients, sender addresses, subject lines, or body content.\n- Send only after the user supplies or confirms every recipient and message.\n- For batch sends, confirm the full recipient/message set before calling a send tool.\n- Use a send-capable `smx_mbx_` key or owner-approved Sending-resource `smx_agent_` token for the Sending API.\n- A durable agent profile is read/receive-only. Do not treat its stored credential as send-capable.\n- Before owner acceptance and sending approval, agent-profile sends fail closed. After approval, the CLI exchanges and caches a one-hour delegated `email.send` token automatically.\n- The self-registered inbox is capped at 500 MiB before approval. Sending approval raises it to 5 GiB first; revoking delegated sending later does not shrink it.\n\n## Choose the send path\n\n| User task | Efficient default |\n| ----------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |\n| One outbound email | `POST /emails/send`, MCP `sending_send_email`, CLI `sending:send`, or SDK `sendingSendEmail`. |\n| More than one independent outbound email | Batch by default: `POST /emails/send/batch`, MCP `sending_send_email_batch`, CLI `sending:send:batch`, or SDK `sendingSendEmailBatch`. |\n| Sending API attachment file | Upload first with `sending_upload_attachment`, `sending_create_attachment_upload`, CLI `--attach`, or SDK file helpers; send by `attachment_id`. |\n| Replying while working inside one mailbox | Use mailbox send from `sendmux-mailbox-agent` when the workflow is mailbox-centred. |\n| Existing app only supports SMTP | Use SMTP only because the existing tool requires it. For new agent or app integrations, prefer the HTTP Sending API. |\n\nBatch sends accept up to 100 messages. A batch response can partially succeed, so inspect every result item.\n\n## Required JSON shape\n\nSingle send body:\n\n```json\n{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n}\n```\n\nRequired fields: `from`, `to`, `subject`, `html_body`.\n\nUseful optional fields:\n\n- `text_body`: plain text alternative.\n- `cc`, `bcc`: arrays of recipients, max 100 each.\n- `reply_to`: one address object.\n- `return_path`: envelope sender for bounce handling.\n- `custom_headers`: custom `X-*` headers.\n- `attachments`: up to 10 items. Prefer uploaded refs `{ \"attachment_id\": \"att_...\" }`. Inline compatibility form uses `filename` plus base64 `content`, optional `type`, and `encoding: \"base64\"`.\n\nFor real local files, do not ask the model to produce base64. Route attachment-heavy work to `sendmux-attachments`; use CLI `--attach`, SDK file helpers, `sending_upload_attachment`, or delegated `sending_create_attachment_upload`, then pass `attachment_id` refs. Sending uploads cap each file at 18 MiB and the final sent message at 25 MB. Mailbox `blob_id` refs are for mailbox sends, not Sending API sends.\n\nBatch send body:\n\n```json\n{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Local file upload before send: `sending_upload_attachment` with `file_path`.\n- Hosted or shell-capable upload before send: `sending_create_attachment_upload`, then `PUT` bytes to the returned URL with the returned headers and no Sendmux API key.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nInclude an idempotency key when the client exposes the header parameter. If the MCP client does not expose headers clearly, use CLI, SDK, or direct HTTP for retry-sensitive sends. For attachments through MCP, use `sendmux-attachments` so the agent chooses `file_path`, presigned upload, or tiny inline base64 correctly.\n\n## CLI\n\nFor a self-registered agent, use its profile instead of copying credentials:\n\n```bash\nsendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json\n```\n\nThe owner must already have accepted the invitation and approved sending. The CLI obtains and caches the short-lived delegated token; the durable read credential is not used directly by the Sending API.\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.message_id, response.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl -X POST https://smtp.sendmux.ai/api/v1/emails/send \\\n -H \"Authorization: Bearer $SENDMUX_MBX_KEY\" \\\n -H \"Content-Type: application/json\" \\\n -H \"Idempotency-Key: $IDEMPOTENCY_KEY\" \\\n -d @sendmux-email.json\n```\n\n## Responses and errors\n\nSingle send success returns a `200` success envelope with:\n\n- `data.message_id`: `eml_...`\n- `data.status`: `queued`\n\nBatch success returns a `200` success envelope with:\n\n- `data.summary.total`\n- `data.summary.queued`\n- `data.summary.failed`\n- `data.results[]` containing `index`, `status`, `message_id`, and optional `error`\n\nHandle these errors deliberately:\n\n- `401`: missing, invalid, or revoked key.\n- `402`: insufficient credits.\n- `403`: key lacks `email.send`, is not allowed for the sender, or uses the wrong surface.\n- `409`: idempotency conflict.\n- `413`: request body exceeds 25 MB.\n- `422`: validation failed; read `error.errors`.\n- `429` or `503`: retry according to response headers.\n\n## Routing\n\n- Setup/auth first call: `sendmux-getting-started`.\n- Attachment file paths, presigned upload URLs, and download URLs: `sendmux-attachments`.\n- Mailbox-centred replies: `sendmux-mailbox-agent`.\n- CLI-only details: `sendmux-cli`.\n- Cheapest-call decisions: `sendmux-token-efficient-usage`.\n\nFile v1.0.5:_meta.json\n\n{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.5\",\n \"publishedAt\": 1788242759278\n}\n\nFile v1.0.5:skill-card.md\n\n## Description:\n\nSend one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\n\nThis skill is ready for commercial/non-commercial use.\n\n## Publisher:\n\n[sendmux.ai](https://clawhub.ai/user/sendmux.ai)\n\n### License/Terms of Use:\n\nMIT-0\n\n## Use Case:\n\nDevelopers and external users use this skill to prepare and send single or batch outbound emails through Sendmux using MCP, CLI, SDK, or HTTP paths with confirmation, credential-safety, attachment, and idempotency guidance.\n\n### Deployment Geography for Use:\n\nGlobal\n\n## Known Risks and Mitigations:\n\nRisk: An agent could send email to unintended recipients or with incorrect message content.\n\nMitigation: Confirm the sender, recipients, subject, body, attachments, and batch list before any send operation.\n\nRisk: Sendmux API or mailbox credentials could be exposed if pasted into chat.\n\nMitigation: Use scoped Sendmux credentials, environment variables, agent profiles, or delegated tokens instead of sharing secrets in conversation.\n\nRisk: Retries could duplicate sends or produce idempotency conflicts.\n\nMitigation: Use one stable Idempotency-Key per logical email or batch and handle 409 conflicts deliberately.\n\nRisk: Batch sends, attachments, or oversized requests can fail partially or exceed service limits.\n\nMitigation: Inspect every batch result and use supported attachment upload paths while respecting documented message and file-size limits.\n\n## Reference(s):\n\n- [Sendmux skills repository](https://github.com/Sendmux/skills)\n- [Sendmux Sending API endpoint](https://smtp.sendmux.ai/api/v1/emails/send)\n\n## Skill Output:\n\n**Output Type(s):** [Text, Markdown, Code, Shell commands, Configuration, Guidance]\n\n**Output Format:** [Markdown with JSON, bash, TypeScript, and HTTP examples]\n\n**Output Parameters:** [1D]\n\n**Other Properties Related to Output:** [Requires user confirmation of sender, recipients, subject, body, attachments, and batch list before sending.]\n\n## Skill Version(s):\n\n1.0.5 (source: server release evidence)\n\n## Ethical Considerations:\n\nUsers should evaluate whether this skill is appropriate for their environment, review any generated or modified files before relying on them, and apply their organization's safety, security, and compliance requirements before deployment.\n\nArchive v1.0.4: 3 files, 5078 bytes\n\nFiles: skill-card.md (2793b), SKILL.md (9132b), _meta.json (137b)\n\nFile v1.0.4:SKILL.md\n\n---\nname: \"sendmux-send-email\"\ndescription: \"Send one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\"\nversion: \"1.3.0\"\nmetadata:\n openclaw:\n skillKey: \"sendmux-send-email\"\n homepage: \"https://github.com/Sendmux/skills\"\n primaryEnv: \"SENDMUX_API_KEY\"\n envVars:\n - name: \"SENDMUX_API_KEY\"\n required: false\n description: \"Optional Sendmux API key or scoped agent token used by CLI, SDK, HTTP, or MCP examples.\"\n - name: \"SENDMUX_MBX_KEY\"\n required: false\n description: \"Optional Sendmux mailbox key for Mailbox and send-capable mailbox workflows.\"\n---\n\n# Sendmux send email\n\n## ClawHub account note\n\nThis ClawHub skill connects OpenClaw agents to Sendmux. Some workflows require a Sendmux account and an appropriate Sendmux API key or agent token. Sendmux account usage is external to ClawHub; do not ask users to paste secrets into chat.\n\nUse this skill when the user is ready to send outbound email through Sendmux or needs code/commands for sending.\n\n## Safety first\n\n- Do not ask the user to paste an API key.\n- Do not invent recipients, sender addresses, subject lines, or body content.\n- Send only after the user supplies or confirms every recipient and message.\n- For batch sends, confirm the full recipient/message set before calling a send tool.\n- Use a send-capable `smx_mbx_` key or owner-approved Sending-resource `smx_agent_` token for the Sending API.\n- Do not use a pre-claim `smx_agent_` token for sending. Pre-claim self-registered agent tokens have `mailbox.read` and `email.receive`, not `email.send`.\n- If using a self-registered agent, obtain the Sending-resource `smx_agent_` token by exchanging the saved `claim_token` after owner approval with `resource=https://smtp.sendmux.ai/api/v1`.\n\n## Choose the send path\n\n| User task | Efficient default |\n| ----------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |\n| One outbound email | `POST /emails/send`, MCP `sending_send_email`, CLI `sending:send`, or SDK `sendingSendEmail`. |\n| More than one independent outbound email | Batch by default: `POST /emails/send/batch`, MCP `sending_send_email_batch`, CLI `sending:send:batch`, or SDK `sendingSendEmailBatch`. |\n| Sending API attachment file | Upload first with `sending_upload_attachment`, `sending_create_attachment_upload`, CLI `--attach`, or SDK file helpers; send by `attachment_id`. |\n| Replying while working inside one mailbox | Use mailbox send from `sendmux-mailbox-agent` when the workflow is mailbox-centred. |\n| Existing app only supports SMTP | Use SMTP only because the existing tool requires it. For new agent or app integrations, prefer the HTTP Sending API. |\n\nBatch sends accept up to 100 messages. A batch response can partially succeed, so inspect every result item.\n\n## Required JSON shape\n\nSingle send body:\n\n```json\n{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n}\n```\n\nRequired fields: `from`, `to`, `subject`, `html_body`.\n\nUseful optional fields:\n\n- `text_body`: plain text alternative.\n- `cc`, `bcc`: arrays of recipients, max 100 each.\n- `reply_to`: one address object.\n- `return_path`: envelope sender for bounce handling.\n- `custom_headers`: custom `X-*` headers.\n- `attachments`: up to 10 items. Prefer uploaded refs `{ \"attachment_id\": \"att_...\" }`. Inline compatibility form uses `filename` plus base64 `content`, optional `type`, and `encoding: \"base64\"`.\n\nFor real local files, do not ask the model to produce base64. Route attachment-heavy work to `sendmux-attachments`; use CLI `--attach`, SDK file helpers, `sending_upload_attachment`, or delegated `sending_create_attachment_upload`, then pass `attachment_id` refs. Sending uploads cap each file at 18 MiB and the final sent message at 25 MB. Mailbox `blob_id` refs are for mailbox sends, not Sending API sends.\n\nBatch send body:\n\n```json\n{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Local file upload before send: `sending_upload_attachment` with `file_path`.\n- Hosted or shell-capable upload before send: `sending_create_attachment_upload`, then `PUT` bytes to the returned URL with the returned headers and no Sendmux API key.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nInclude an idempotency key when the client exposes the header parameter. If the MCP client does not expose headers clearly, use CLI, SDK, or direct HTTP for retry-sensitive sends. For attachments through MCP, use `sendmux-attachments` so the agent chooses `file_path`, presigned upload, or tiny inline base64 correctly.\n\n## CLI\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.message_id, response.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl -X POST https://smtp.sendmux.ai/api/v1/emails/send \\\n -H \"Authorization: Bearer $SENDMUX_MBX_KEY\" \\\n -H \"Content-Type: application/json\" \\\n -H \"Idempotency-Key: $IDEMPOTENCY_KEY\" \\\n -d @sendmux-email.json\n```\n\n## Responses and errors\n\nSingle send success returns a `200` success envelope with:\n\n- `data.message_id`: `eml_...`\n- `data.status`: `queued`\n\nBatch success returns a `200` success envelope with:\n\n- `data.summary.total`\n- `data.summary.queued`\n- `data.summary.failed`\n- `data.results[]` containing `index`, `status`, `message_id`, and optional `error`\n\nHandle these errors deliberately:\n\n- `401`: missing, invalid, or revoked key.\n- `402`: insufficient credits.\n- `403`: key lacks `email.send`, is not allowed for the sender, or uses the wrong surface.\n- `409`: idempotency conflict.\n- `413`: request body exceeds 25 MB.\n- `422`: validation failed; read `error.errors`.\n- `429` or `503`: retry according to response headers.\n\n## Routing\n\n- Setup/auth first call: `sendmux-getting-started`.\n- Attachment file paths, presigned upload URLs, and download URLs: `sendmux-attachments`.\n- Mailbox-centred replies: `sendmux-mailbox-agent`.\n- CLI-only details: `sendmux-cli`.\n- Cheapest-call decisions: `sendmux-token-efficient-usage`.\n\nFile v1.0.4:_meta.json\n\n{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.4\",\n \"publishedAt\": 1783569527642\n}\n\nFile v1.0.4:skill-card.md\n\n## Description:Hello.
\",\n \"text_body\": \"Hello.\"\n}\n```\n\nRequired fields: `from`, `to`, `subject`, `html_body`.\n\nUseful optional fields:\n\n- `text_body`: plain text alternative.\n- `cc`, `bcc`: arrays of recipients, max 100 each.\n- `reply_to`: one address object.\n- `return_path`: envelope sender for bounce handling.\n- `custom_headers`: custom `X-*` headers.\n- `attachments`: up to 10 items. Prefer uploaded refs `{ \"attachment_id\": \"att_...\" }`. Inline compatibility form uses `filename` plus base64 `content`, optional `type`, and `encoding: \"base64\"`.\n\nFor real local files, do not ask the model to produce base64. Route attachment-heavy work to `sendmux-attachments`; use CLI `--attach`, SDK file helpers, `sending_upload_attachment`, or delegated `sending_create_attachment_upload`, then pass `attachment_id` refs. Sending uploads cap each file at 18 MiB and the final sent message at 25 MB. Mailbox `blob_id` refs are for mailbox sends, not Sending API sends.\n\nBatch send body:\n\n```json\n{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Local file upload before send: `sending_upload_attachment` with `file_path`.\n- Hosted or shell-capable upload before send: `sending_create_attachment_upload`, then `PUT` bytes to the returned URL with the returned headers and no Sendmux API key.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nInclude an idempotency key when the client exposes the header parameter. If the MCP client does not expose headers clearly, use CLI, SDK, or direct HTTP for retry-sensitive sends. For attachments through MCP, use `sendmux-attachments` so the agent chooses `file_path`, presigned upload, or tiny inline base64 correctly.\n\n## CLI\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.message_id, response.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl -X POST https://smtp.sendmux.ai/api/v1/emails/send \\\n -H \"Authorization: Bearer $SENDMUX_MBX_KEY\" \\\n -H \"Content-Type: application/json\" \\\n -H \"Idempotency-Key: $IDEMPOTENCY_KEY\" \\\n -d @sendmux-email.json\n```\n\n## Responses and errors\n\nSingle send success returns a `200` success envelope with:\n\n- `data.message_id`: `eml_...`\n- `data.status`: `queued`\n\nBatch success returns a `200` success envelope with:\n\n- `data.summary.total`\n- `data.summary.queued`\n- `data.summary.failed`\n- `data.results[]` containing `index`, `status`, `message_id`, and optional `error`\n\nHandle these errors deliberately:\n\n- `401`: missing, invalid, or revoked key.\n- `402`: insufficient credits.\n- `403`: key lacks `email.send`, is not allowed for the sender, or uses the wrong surface.\n- `409`: idempotency conflict.\n- `413`: request body exceeds 25 MB.\n- `422`: validation failed; read `error.errors`.\n- `429` or `503`: retry according to response headers.\n\n## Routing\n\n- Setup/auth first call: `sendmux-getting-started`.\n- Attachment file paths, presigned upload URLs, and download URLs: `sendmux-attachments`.\n- Mailbox-centred replies: `sendmux-mailbox-agent`.\n- CLI-only details: `sendmux-cli`.\n- Cheapest-call decisions: `sendmux-token-efficient-usage`.\n\nFile v1.0.3:_meta.json\n\n{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.3\",\n \"publishedAt\": 1783561592367\n}\n\nFile v1.0.3:skill-card.md\n\n## Description:Hello.
\",\n \"text_body\": \"Hello.\"\n}\n```\n\nRequired fields: `from`, `to`, `subject`, `html_body`.\n\nUseful optional fields:\n\n- `text_body`: plain text alternative.\n- `cc`, `bcc`: arrays of recipients, max 100 each.\n- `reply_to`: one address object.\n- `return_path`: envelope sender for bounce handling.\n- `custom_headers`: custom `X-*` headers.\n- `attachments`: up to 10 items. Prefer uploaded refs `{ \"attachment_id\": \"att_...\" }`. Inline compatibility form uses `filename` plus base64 `content`, optional `type`, and `encoding: \"base64\"`.\n\nFor real local files, do not ask the model to produce base64. Route attachment-heavy work to `sendmux-attachments`; use CLI `--attach`, SDK file helpers, `sending_upload_attachment`, or delegated `sending_create_attachment_upload`, then pass `attachment_id` refs. Sending uploads cap each file at 18 MiB and the final sent message at 25 MB. Mailbox `blob_id` refs are for mailbox sends, not Sending API sends.\n\nBatch send body:\n\n```json\n{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}\n```\n\n## Idempotency\n\nAdd `Idempotency-Key` to every send that may be retried. Use one stable key per logical email or batch.\n\n- Same key and same body: returns the cached response for 24 hours.\n- Same key and different body: returns `409 idempotency_conflict`.\n- Keep keys under 255 characters.\n\n## MCP\n\nUse MCP when the user's agent already has the Sending server connected:\n\n- One message: `sending_send_email`.\n- Multiple messages: `sending_send_email_batch`.\n- Local file upload before send: `sending_upload_attachment` with `file_path`.\n- Hosted or shell-capable upload before send: `sending_create_attachment_upload`, then `PUT` bytes to the returned URL with the returned headers and no Sendmux API key.\n- Metadata check for a temporary uploaded attachment: `sending_get_attachment`.\n\nInclude an idempotency key when the client exposes the header parameter. If the MCP client does not expose headers clearly, use CLI, SDK, or direct HTTP for retry-sensitive sends. For attachments through MCP, use `sendmux-attachments` so the agent chooses `file_path`, presigned upload, or tiny inline base64 correctly.\n\n## CLI\n\nOne email:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json\n```\n\nBatch:\n\n```bash\nSENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json\n```\n\nUse `--attach ./file.pdf` for local files; the CLI uploads bytes first and injects `attachment_id` refs before sending. Use `--body-file` for larger JSON payloads or already-prepared Sending API attachment objects.\n\n## TypeScript SDK\n\nOne email:\n\n```ts\nimport { createSendingClient, sendingSendEmail } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmail({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n from: { email: \"sender@example.com\", name: \"Sender Name\" },\n to: { email: \"recipient@example.com\", name: \"Recipient Name\" },\n subject: \"Subject line\",\n html_body: \"Hello.
\",\n text_body: \"Hello.\",\n },\n});\n\nconsole.log(response.data.message_id, response.data.status);\n```\n\nBatch:\n\n```ts\nimport { createSendingClient, sendingSendEmailBatch } from \"@sendmux/sending\";\n\nconst client = createSendingClient({ apiKey: process.env.SENDMUX_API_KEY! });\n\nconst response = await sendingSendEmailBatch({\n client,\n headers: { \"Idempotency-Key\": idempotencyKey },\n body: {\n messages,\n },\n});\n\nfor (const result of response.data.results) {\n console.log(result.index, result.status, result.message_id, result.error);\n}\n```\n\n## Direct HTTP\n\nUse direct HTTP only when MCP, CLI, or SDK is unavailable:\n\n```bash\ncurl -X POST https://smtp.sendmux.ai/api/v1/emails/send \\\n -H \"Authorization: Bearer $SENDMUX_MBX_KEY\" \\\n -H \"Content-Type: application/json\" \\\n -H \"Idempotency-Key: $IDEMPOTENCY_KEY\" \\\n -d @sendmux-email.json\n```\n\n## Responses and errors\n\nSingle send success returns a `200` success envelope with:\n\n- `data.message_id`: `eml_...`\n- `data.status`: `queued`\n\nBatch success returns a `200` success envelope with:\n\n- `data.summary.total`\n- `data.summary.queued`\n- `data.summary.failed`\n- `data.results[]` containing `index`, `status`, `message_id`, and optional `error`\n\nHandle these errors deliberately:\n\n- `401`: missing, invalid, or revoked key.\n- `402`: insufficient credits.\n- `403`: key lacks `email.send`, is not allowed for the sender, or uses the wrong surface.\n- `409`: idempotency conflict.\n- `413`: request body exceeds 25 MB.\n- `422`: validation failed; read `error.errors`.\n- `429` or `503`: retry according to response headers.\n\n## Routing\n\n- Setup/auth first call: `sendmux-getting-started`.\n- Attachment file paths, presigned upload URLs, and download URLs: `sendmux-attachments`.\n- Mailbox-centred replies: `sendmux-mailbox-agent`.\n- CLI-only details: `sendmux-cli`.\n- Cheapest-call decisions: `sendmux-token-efficient-usage`.\n\nFile v1.0.2:_meta.json\n\n{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.2\",\n \"publishedAt\": 1783483690652\n}\n\nFile v1.0.2:skill-card.md\n\n## Description:Hello.
\",\n \"text_body\": \"Hello.\"\n}"},{"language":"http","snippet":"POST /emails/send/batch HTTP/1.1\nAuthorization: Bearer $SENDMUX_MBX_KEY\nContent-Type: application/json\nIdempotency-Key: $IDEMPOTENCY_KEY"},{"language":"json","snippet":"{\n \"messages\": [\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"alice@example.com\" },\n \"subject\": \"Hello Alice\",\n \"html_body\": \"Hi Alice.
\"\n },\n {\n \"from\": { \"email\": \"sender@example.com\" },\n \"to\": { \"email\": \"bob@example.com\" },\n \"subject\": \"Hello Bob\",\n \"html_body\": \"Hi Bob.
\"\n }\n ]\n}"},{"language":"bash","snippet":"sendmux sending:send \\\n --profile my-agent \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-email.json \\\n --json"},{"language":"bash","snippet":"SENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body '{\n \"from\": { \"email\": \"sender@example.com\", \"name\": \"Sender Name\" },\n \"to\": { \"email\": \"recipient@example.com\", \"name\": \"Recipient Name\" },\n \"subject\": \"Subject line\",\n \"html_body\": \"Hello.
\",\n \"text_body\": \"Hello.\"\n }' \\\n --json"},{"language":"bash","snippet":"SENDMUX_API_KEY=\"$SENDMUX_MBX_KEY\" sendmux sending:send:batch \\\n --idempotency-key \"$IDEMPOTENCY_KEY\" \\\n --body-file ./sendmux-batch.json \\\n --json"}],"parameters":null,"dependencies":[],"permissions":[],"extractedFiles":[{"path":"SKILL.md","content":"---\nname: \"sendmux-send-email\"\ndescription: \"Send one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\"\nversion: \"1.7.1\"\nmetadata:\n openclaw:\n skillKey: \"sendmux-send-email\"\n homepage: \"https://github.com/Sendmux/skills\"\n primaryEnv: \"SENDMUX_API_KEY\"\n envVars:\n - name: \"SENDMUX_API_KEY\"\n required: false\n description: \"Optional Sendmux API key or scoped agent token used by CLI, SDK, HTTP, or MCP examples.\"\n - name: \"SENDMUX_MBX_KEY\"\n required: false\n description: \"Optional Sendmux mailbox key for Mailbox and send-capable mailbox workflows.\"\n---\n\n# Sendmux send email\n\n## ClawHub account note\n\nThis ClawHub skill connects OpenClaw agents to Sendmux. Some workflows require a Sendmux account and an appropriate Sendmux API key or agent token. Sendmux account usage is external to ClawHub; do not ask users to paste secrets into chat.\n\nUse this skill when the user is ready to send outbound email through Sendmux or needs code/commands for sending.\n\n## Safety first\n\n- Do not ask the user to paste an API key.\n- Do not invent recipients, sender addresses, subject lines, or body content.\n- Send only after the user supplies or confirms every recipient and message.\n- For batch sends, confirm the full recipient/message set before calling a send tool.\n- Use a send-capable `smx_mbx_` key, owner-approved Sending-resource `smx_agent_` token, or REST OAuth grant with Sending access and `email.send` for the Sending HTTP API. SMTP requires a send-capable API key; OAuth access tokens are not SMTP or IMAP passwords.\n\nFor an agent-profile before/after approval answer, cover the complete lifecycle:\n\n| State | Required explanation |\n| --- | --- |\n| Before owner acceptance and sending approval | The durable credential is read/receive-only, sends fail closed, and the self-registered inbox is capped at 500 MiB. |\n| After sending approval | Storage rises to at least 5 GiB. The CLI automatically exchanges for a one-hour delegated `email.send` token and caches it only until near expiry; the sender supplies one stable `--idempotency-key` per logical send. |\n| After sending revocation | Sending becomes unavailable again, but revocation does not itself change the current inbox storage allocation. |\n\nSending approval supplies the required authority; it does not guarantee that a later request will pass validation or be accepted for delivery.\n\n## Choose the send path\n\n| User task | Efficient default |\n| ----------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |\n| One outbound email | `POST /emails/send`, MCP `sending_send_email`, CLI `sending:send`, or SDK `sendingSe"},{"path":"_meta.json","content":"{\n \"ownerId\": \"kn77z51yqhw8mt9vjfkpt8w74989rfb3\",\n \"slug\": \"sendmux-send-email\",\n \"version\": \"1.0.11\",\n \"publishedAt\": 1790915001981\n}"},{"path":"skill-card.md","content":"## Description:\n\nSend one or many emails through Sendmux using approved mailbox or agent credentials, idempotency keys, attachments, MCP, CLI, SDKs, or HTTP.\n\nThis skill is ready for commercial/non-commercial use.\n\n## Publisher:\n\n[sendmux.ai](https://clawhub.ai/user/sendmux.ai)\n\n### License/Terms of Use:\n\nMIT-0\n\n## Use Case:\n\nOpenClaw users and developers use this skill to prepare or send individual and batch emails through Sendmux, including messages with attachments, after confirming the full message details.\n\n### Deployment Geography for Use:\n\nGlobal\n\n## Known Risks and Mitigations:\n\nRisk: Outbound messages could reach an unintended recipient or disclose sensitive content or attachments.\n\nMitigation: Review and confirm the sender, every recipient, subject, body, and attachment before each send or batch.\n\nRisk: Sendmux credentials could be exposed or grant broader sending access than needed.\n\nMitigation: Use scoped credentials and keep secrets out of chat.\n\n## Reference(s):\n\n- [ClawHub skill release](https://clawhub.ai/sendmux.ai/skills/sendmux-send-email)\n- [Sendmux skills homepage (declared in skill metadata)](https://github.com/Sendmux/skills)\n\n## Skill Output:\n\n**Output Type(s):** [Guidance, Shell commands, Code]\n\n**Output Format:** [Markdown with JSON, shell, HTTP, and TypeScript examples]\n\n**Output Parameters:** [1D]\n\n**Other Properties Related to Output:** [Sending requires confirmed message details and appropriate Sendmux authorization.]\n\n## Skill Version(s):\n\n1.0.11 (source: ClawHub release metadata; skill frontmatter: 1.7.1)\n\n## Ethical Considerations:\n\nUsers should evaluate whether this skill is appropriate for their environment, review any generated or modified files before relying on them, and apply their organization's safety, security, and compliance requirements before deployment."}],"languages":[],"docsSourceLabel":"CLAWHUB","editorialOverview":null,"editorialQuality":{"score":100,"threshold":65,"status":"thin","wordCount":1362,"uniquenessScore":43,"reasons":["uniqueness-below-45"]}},"media":{"evidence":{"source":"no-media","verified":false,"confidence":"low","updatedAt":"2026-10-10T06:14:46.961Z","emptyReason":"No screenshots, media assets, or demo links are available."},"primaryImageUrl":null,"mediaAssetCount":0,"assets":[],"demoUrl":null},"ownerResources":{"evidence":{"source":"unclaimed","verified":false,"confidence":"low","updatedAt":"2026-10-10T06:14:46.961Z","emptyReason":"This page has not been claimed by the agent owner."},"hasCustomPage":false,"customPageUpdatedAt":null,"customLinks":[],"structuredLinks":{"docsUrl":null,"demoUrl":null,"supportUrl":null,"pricingUrl":null,"statusUrl":null},"customPage":null},"relatedAgents":{"evidence":{"source":"protocol-neighbors","verified":false,"confidence":"medium","updatedAt":"2026-10-10T10:44:07.780Z","emptyReason":null},"items":[{"id":"8ebccd8e-3863-4187-8355-c3f14e1f9edf","entityType":"agent","canonicalPath":"/agent/iofficeai-aionui","slug":"iofficeai-aionui","name":"AionUi","description":"Free, local, open-source 24/7 Cowork app and OpenClaw for Gemini CLI, Claude Code, Codex, OpenCode, Qwen Code, Goose CLI, Auggie, and more | 🌟 Star if you like it!","url":"https://github.com/iOfficeAI/AionUi","homepage":"https://www.aionui.com","source":"GITHUB_REPOS","protocols":["MCP","OPENCLAW"],"capabilities":[],"safetyScore":100,"overallRank":70,"updatedAt":"2026-10-09T19:11:12.944Z","createdAt":"2026-02-25T03:38:16.584Z","downloads":null},{"id":"b917f68a-ebff-438e-84f8-3f4b2494c0bc","entityType":"agent","canonicalPath":"/agent/activepieces-activepieces","slug":"activepieces-activepieces","name":"activepieces","description":"AI Agents & MCPs & AI Workflow Automation • (~400 MCP servers for AI agents) • AI Automation / AI Agent with MCPs • AI Workflows & AI Agents • MCPs for AI Agents","url":"https://github.com/activepieces/activepieces","homepage":"https://www.activepieces.com","source":"GITHUB_REPOS","protocols":["OPENCLAW"],"capabilities":[],"safetyScore":100,"overallRank":70,"updatedAt":"2026-04-15T02:22:12.426Z","createdAt":"2026-02-25T03:38:12.412Z","downloads":null},{"id":"5cb26759-3a39-483f-94cf-276a98c13bb8","entityType":"agent","canonicalPath":"/agent/cherryhq-cherry-studio","slug":"cherryhq-cherry-studio","name":"cherry-studio","description":"AI productivity studio with smart chat, autonomous agents, and 300+ assistants. 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