API Reference

Complete API reference for HeliosSend Client API.

Base URL

https://client.heliossend.com

Authentication

Authorization Header

All requests require authentication via the Authorization header

Authorization: cs_YOUR_API_KEY

Include your API Key (starting with cs_) in the Authorization header of every request.

Endpoints

POST /send

Send an email

Request Headers

Content-Type: application/json
Authorization: cs_YOUR_API_KEY

Request Body

{
  "from": "string (email, required)",
  "to": ["array of email strings, required"],
  "cc": ["array of email strings, optional"],
  "bcc": ["array of email strings, optional"],
  "subject": "string (required)",
  "html": "string (optional)",
  "text": "string (optional)",
  "template_id": "string (optional)",
  "substitutions": { "object (optional)" },
  "metadata": { "object (optional)" }
}

Response (200 OK)

{
  "message_id": "string",
  "status": "string"
}

Error Responses

401: Invalid user credentials
403: Account not active
500: Failed to send email

GET /status/{message_id}

Get the status of an email message

URL Parameters

message_id - The message ID returned from the send endpoint

Response (200 OK)

{
  "id": "string",
  "status": "string",
  "message_id": "string | null",
  "created_at": "ISO 8601 datetime",
  "updated_at": "ISO 8601 datetime"
}

Error Responses

404: Message not found

Status Values

Message Status

Possible values for the status field

queued

Message is queued for sending

sent

Message has been sent to AWS SES

failed

Message sending failed

Rate Limits

API Limits

Rate limits are determined by your subscription tier and plan. Contact support for information about your specific limits.