> ## Documentation Index
> Fetch the complete documentation index at: https://developer.effilink.co/llms.txt
> Use this file to discover all available pages before exploring further.

# EffiLink REST API: Cloud Messaging for Email and SMS

> EffiLink is a cloud messaging REST API for sending transactional email, marketing campaigns, and SMS with real-time delivery tracking and webhooks.

EffiLink gives you a single REST API to send transactional emails, run marketing campaigns, deliver SMS messages, and receive real-time engagement events via webhooks. All of this runs on EffiLink's infrastructure at `api.effilink.co`, so you focus on your product, not on deliverability.

## What you can do with EffiLink

<CardGroup cols={2}>
  <Card title="Transactional Email" icon="envelope" href="/docs/transactional-email">
    Send triggered emails like order confirmations, password resets, and shipping notifications.
  </Card>

  <Card title="Marketing Campaigns" icon="bullhorn" href="/docs/campaign-email">
    Create and deliver newsletters, promotions, and announcements to contact lists.
  </Card>

  <Card title="SMS" icon="mobile" href="/docs/sms-send">
    Send individual or bulk SMS messages for notifications and promotions.
  </Card>

  <Card title="Webhooks" icon="webhook" href="/docs/webhooks">
    Receive real-time events for every delivery, open, click, bounce, and unsubscribe.
  </Card>
</CardGroup>

## API fundamentals

EffiLink provides geographically distributed API endpoints to ensure high availability and optimal access performance. Please use the endpoint closest to your application's deployment region:

* Mainland China:
  ```text theme={null}
  https://api.effilink.co
  ```
* Hong Kong China:
  ```text theme={null}
  https://hk-api.effilink.co
  ```
* Europe:
  ```text theme={null}
  https://eu-api.effilink.co 
  ```

For the best latency and reliability, we recommend selecting the endpoint that is geographically closest to your users or application servers.

Every request must:

* Be sent over **HTTPS**
* Use `Content-Type: application/json`
* Include an authentication header (`ApiKey` or `OAuth`)

<Note>
  Parameter names are **case-sensitive**. All request and response data uses UTF-8 encoding.
</Note>

## HTTP response codes

| Code | Status             | Meaning                                           |
| ---- | ------------------ | ------------------------------------------------- |
| 200  | OK                 | Request succeeded                                 |
| 400  | Bad Request        | Invalid data format or missing required parameter |
| 404  | Not Found          | Endpoint does not exist                           |
| 405  | Method Not Allowed | Use GET or POST as specified                      |
| 429  | Too Many Requests  | Rate limit exceeded                               |
|      |                    |                                                   |

## Pagination

List and search endpoints return paginated results. Use these query parameters to navigate pages:

| Parameter   | Type    | Description                    |
| ----------- | ------- | ------------------------------ |
| `pageSize`  | integer | Number of records per page     |
| `pageIndex` | integer | Page number, starting from `1` |

## Next steps

<CardGroup cols={2}>
  <Card title="Quick Start" icon="rocket" href="/docs/quickstart">
    Send your first email in under 5 minutes.
  </Card>

  <Card title="Authentication" icon="key" href="/docs/authentication">
    Learn how to authenticate API requests.
  </Card>
</CardGroup>