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

# HTTP status codes

> Status codes returned by the Newsletter API.

| Code  | Meaning                                                                |
| ----- | ---------------------------------------------------------------------- |
| `200` | OK — query or update successful.                                       |
| `201` | Created — resource created.                                            |
| `400` | Bad request — malformed JSON, invalid list or invalid `status` filter. |
| `401` | Unauthorized — missing or invalid API key.                             |
| `403` | Forbidden — API access disabled or module capability disabled.         |
| `404` | Not found — subscriber does not exist.                                 |
| `413` | Payload too large.                                                     |
| `415` | Unsupported media type — use `application/json`.                       |
| `422` | Validation error — field-level errors.                                 |
| `429` | Rate limit exceeded or temporary lockout.                              |

See [Response format](/api/response-format) for the error envelope, and
[Rate limits](/api/rate-limits) for the `429` payload.