API Reference

The Sendbound REST API lets you send transactional email, manage contacts and lists, run campaigns, and configure everything programmatically.

Base URL: https://api.sendbound.com

Authentication

All requests must include your secret API key as a Bearer token:

Authorization: Bearer sk_live_...

Use sk_live_ keys for production. You can create and revoke keys from Settings → API Keys.

Resource	Description
Send Email	Send a transactional email to one or more recipients
Batch Send	Send up to 100 different emails in one API call
Emails	Retrieve sent emails and check delivery status
Contacts	Full CRUD, tags, suppression, CSV import/export
Segments	Dynamic and static contact segments
Campaigns	Bulk sends to segments with scheduling and A/B testing
Templates	Reusable email templates with `{{variables}}`
Domains	Add and verify sending domains
API Keys	Create and revoke API keys
Webhooks	Receive delivery events in real time
MCP Server	Build AI agents that use email

Successful responses return HTTP 2xx with a JSON body. Error responses follow this shape:

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Human-readable description",
    "statusCode": 400
  }
}

HTTP	Code	Description
400	`VALIDATION_ERROR`	Missing or invalid request field
401	`MISSING_AUTH`	No Authorization header
401	`INVALID_API_KEY`	Key not found or revoked
402	`PAYMENT_REQUIRED`	Plan limit reached
403	`NOT_ALLOWED`	Operation not permitted
404	`NOT_FOUND`	Resource does not exist
409	`CONFLICT`	Resource already exists
429	`RATE_LIMIT_EXCEEDED`	Too many requests — back off and retry
5xx	`INTERNAL_ERROR`	Server error

The default rate limit is 100 requests / 10 seconds per API key. Bursts above this return 429. Contact support to increase your limit.

List endpoints return a nextCursor field. Pass it as cursor in your next request to fetch the next page:

GET /contacts?limit=50&cursor=eyJpZCI6ImNvbl8w...

When nextCursor is absent, you have reached the last page.