API Documentation

Authentication

All requests to the Multi API require an active API key with proper scope permissions. Provide your key in the Authorization header using the Bearer scheme, or via the X-API-Key header.

Authorization: Bearer rp_live_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

POST

/api/v1/emails

Dispatches a single transactional email into the background queue.

Request Body (JSON)

{
  "from": {
    "email": "noreply@yourdomain.com",
    "name": "Acme Auth"
  },
  "to": [
    { "email": "user@example.com", "name": "John Doe" }
  ],
  "subject": "Your Authentication Code",
  "html": "<h1>Code: 123456</h1>",
  "text": "Code: 123456",
  "open_tracking": true,
  "click_tracking": true,
  "tags": ["auth", "otp"]
}

Response (202 Accepted)

{
  "success": true,
  "data": {
    "message_id": "msg_8b2a19f40e1c2d3e4f5a6b7c",
    "status": "queued",
    "from": "noreply@yourdomain.com",
    "to": ["user@example.com"],
    "created_at": "2026-08-22T22:30:00+00:00"
  }
}

POST

/api/v1/emails/batch

Accepts an array of up to 100 email payloads to dispatch concurrently.

{
  "messages": [
    {
      "from": { "email": "alerts@domain.com" },
      "to": [{ "email": "user1@example.com" }],
      "subject": "System Notice 1",
      "html": "<p>Notice 1</p>"
    },
    {
      "from": { "email": "alerts@domain.com" },
      "to": [{ "email": "user2@example.com" }],
      "subject": "System Notice 2",
      "html": "<p>Notice 2</p>"
    }
  ]
}

Webhooks Verification

Every webhook payload dispatched from Multi contains an X-Signature header containing a Unix timestamp and HMAC-SHA256 signature calculated against your endpoint secret.

X-MultiCronJob-Signature: t=1755901200,v1=5d41402abc4b2a76b9719d911017c592...

Error Handling

The Multi API uses standard HTTP response codes accompanied by structured JSON error payloads.

{
  "success": false,
  "error": {
    "code": "SEND_FAILED",
    "message": "Daily sending limit of 500 emails exceeded. Used: 500."
  }
}