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

# Errors

> HTTP status codes and error object schemas returned by Mailofly.

Mailofly uses conventional HTTP response codes to indicate request success or failure.

***

## Status Codes

| Code                        | Meaning                                          |
| :-------------------------- | :----------------------------------------------- |
| **`200 OK`**                | Request succeeded.                               |
| **`201 Created`**           | Resource created successfully.                   |
| **`400 Bad Request`**       | Missing or malformed parameters.                 |
| **`401 Unauthorized`**      | Missing or invalid API key.                      |
| **`403 Forbidden`**         | Sender domain not verified or permission denied. |
| **`404 Not Found`**         | Requested resource ID does not exist.            |
| **`429 Too Many Requests`** | Rate limit exceeded.                             |
| **`500 Internal Error`**    | Mailofly server issue.                           |

***

## Error Response Body

```json theme={null}
{
  "statusCode": 400,
  "message": "The 'to' field must contain at least one valid email address.",
  "name": "validation_error"
}
```


## Related topics

- [Error 1010](/guides/domains/error-1010.md)
- [mailofly.dev Domain Error](/guides/domains/mailofly-dev-domain-error.md)
- [Introduction](/api/index.md)
- [Domain Mismatch](/guides/domains/domain-mismatch.md)
- [Domain already registered](/guides/domains/domain-already-registered.md)