Action-based email covers triggered, one-to-one sends driven by a user action or system event — order confirmations, password resets, receipts, account alerts. Uses channel type EMAIL with message_type: MESSAGE. Always billed as Basic Message regardless of HTML length or images.

​
Request

​
Authorization
string
required
Bearer <api_key>
​
Idempotency-Key
string
UUID to prevent duplicate sends on retry.

​
Body — inline content

{
  "channel_id": "ch_550e8400e29b41d4a716446655440000",
  "to": "customer@arowana.app",
  "subject": "Order #1234 confirmed",
  "message_type": "MESSAGE",
  "content": {
    "html": "<p>Thank you for your purchase. Your order is confirmed.</p>",
    "text": "Thank you for your purchase. Your order is confirmed."
  }
}
​
channel_id
string
required
Email channel id from the dashboard. Determines the sender domain and identity.
​
to
string
required
Recipient email address. Checked against suppression lists before send.
​
subject
string
required
Email subject line. Required unless the template provides it.
​
message_type
string
required
MESSAGE for action-based sends.
​
content.html
string
HTML body. Provide both html and text for maximum deliverability.
​
content.text
string
Plain text fallback. Used by clients that cannot render HTML.

​
Body — template reference

{
  "channel_id": "ch_550e8400e29b41d4a716446655440000",
  "to": "customer@arowana.app",
  "message_type": "MESSAGE",
  "template_id": "tpl_xxxx",
  "template_version": "3",
  "template_data": {
    "order_number": "1234",
    "customer_name": "Alex"
  }
}
​
template_id
string
Template id from the dashboard. Mutually exclusive with inline content.
​
template_version
string
Specific version to render. Omit to use the latest published version.
​
template_data
object
Variables passed into the template at render time.

​
Responses

{
  "message_id": "msg_e1f2a3b4",
  "status": "queued",
  "created_at": "2026-03-28T09:00:00Z",
  "billing": {
    "channel": "EMAIL",
    "message_type": "basic_message",
    "hold_amount": 0.09,
    "message_price": 0.09,
    "balance": {
      "free": 49.91,
      "reserved": 0.09,
      "total": 50.00
    },
    "tier": {
      "channel": "EMAIL",
      "current": "tier_1",
      "volume_used": 5200
    }
  }
}
​
message_id
string
Message id for GET /v1/messages/{id}, revoke, and webhook correlation.
​
status
string
Initial state — queued. Provider events (delivered, bounced) arrive via webhook.
​
billing.message_type
string
Always basic_message for email sends.
​
billing.hold_amount
number
Balance held; email holds typically resolve quickly after provider confirmation.
​
billing.tier
object