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

# Errors

> Troubleshoot problems using this comprehensive breakdown of all isend.ai API error codes.

## Error Schema

isend.ai uses standard HTTP response codes for success and error responses. Each error is also classified with a specific type for easier debugging.

### `invalid_idempotency_key`

* **Status:** 400
* **Message:** The key must be between 1–256 characters.
* **Suggested Action:** Retry with a valid idempotency key.

### `validation_error`

* **Status:** 400
* **Message:** One or more fields in the request are invalid.
* **Suggested Action:** Review the response message for specific details.

### `missing_api_key`

* **Status:** 401
* **Message:** API key missing from Authorization header.
* **Suggested Action:** Include `Authorization: Bearer YOUR_API_KEY` in your request.

### `restricted_api_key`

* **Status:** 401
* **Message:** API key only allowed to send emails.
* **Suggested Action:** Use a key with full access if performing other actions.

### `invalid_api_key`

* **Status:** 403
* **Message:** The provided API key is invalid.
* **Suggested Action:** Verify or regenerate your API key.

### `testing_restriction`

* **Status:** 403
* **Message:** Emails can only be sent to your own address in testing mode.
* **Suggested Action:** Verify a domain to lift this restriction.

### `not_found`

* **Status:** 404
* **Message:** Endpoint does not exist.
* **Suggested Action:** Ensure the request URL is correct.

### `method_not_allowed`

* **Status:** 405
* **Message:** HTTP method not supported on this endpoint.
* **Suggested Action:** Use the allowed method (GET, POST, etc.) for that endpoint.

### `invalid_idempotent_request`

* **Status:** 409
* **Message:** Same idempotency key used with a different payload.
* **Suggested Action:** Use a unique key or match payload to the original.

### `concurrent_idempotent_requests`

* **Status:** 409
* **Message:** Request in progress for this idempotency key.
* **Suggested Action:** Retry after the initial request completes.

### `invalid_attachment`

* **Status:** 422
* **Message:** Attachment requires either `content` or `path`.
* **Suggested Action:** Include one of those fields when adding attachments.

### `invalid_from_address`

* **Status:** 422
* **Message:** Invalid `from` field format.
* **Suggested Action:** Use `email@domain.com` or `Name <email@domain.com>` format.

### `invalid_access`

* **Status:** 422
* **Message:** Access must be "full\_access" or "sending\_access".
* **Suggested Action:** Use an API key with appropriate access level.

### `invalid_parameter`

* **Status:** 422
* **Message:** A provided parameter is not valid (e.g., malformed UUID).
* **Suggested Action:** Verify the parameter and retry.

### `invalid_region`

* **Status:** 422
* **Message:** Region must be one of: "us-east-1", "eu-west-1", or "sa-east-1".
* **Suggested Action:** Provide a valid supported region.

### `missing_required_field`

* **Status:** 422
* **Message:** Required fields missing from request body.
* **Suggested Action:** Review error message and add the missing fields.

### `daily_quota_exceeded`

* **Status:** 429
* **Message:** Email send quota exceeded for the day.
* **Suggested Action:** Upgrade your plan or wait 24 hours.

### `rate_limit_exceeded`

* **Status:** 429
* **Message:** Too many requests sent too quickly.
* **Suggested Action:** Throttle requests or contact support for increased limits.

### `security_error`

* **Status:** 451
* **Message:** Potential security issue detected.
* **Suggested Action:** Refer to the error message or contact support.

### `application_error`

* **Status:** 500
* **Message:** An internal error occurred.
* **Suggested Action:** Retry later or check status.isend.ai.

### `internal_server_error`

* **Status:** 500
* **Message:** Unexpected server error.
* **Suggested Action:** Retry later or check status.isend.ai.