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HTTP Status Codes

The lemlist API uses standard HTTP status codes to indicate the success or failure of requests:
Status CodeMeaning
200Success - The request was successful
400Bad Request - Invalid parameters or invalid team
401Unauthorized - Authentication is missing or invalid
403Forbidden - User is blocked
404Not Found - Resource does not exist
405Method Not Allowed - HTTP method is not allowed for this endpoint
429Too Many Requests - Rate limit exceeded
500Internal Server Error - An error occurred on the server
For authentication related errors, refer to the Authentication section.

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Common error messages

This indicates that the team associated with your API key is invalid or you don’t have permission to access the requested resource.Common causes
  • The resource belongs to a different team
  • Your API key doesn’t have access to the requested team
  • Invalid team configuration
One or more request parameters are invalid.Common causes
  • Missing required parameters
  • Invalid parameter format
  • Parameter values out of acceptable range
  • Invalid JSON in request body
How to fix: Review the endpoint documentation and ensure all required parameters are provided with correct formatting.
A generic error indicating that the request could not be processed due to client error.Common causes
  • Malformed JSON
  • Invalid data types
  • Logical errors in request data

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Best practices

  1. Always check the response status code before processing the response body
  2. Implement exponential backoff for retrying failed requests
  3. Log error responses for debugging and monitoring
  4. Handle authentication errors by refreshing or validating your API key — see Authentication
  5. Respect rate limits by implementing request throttling — see Rate limits
  6. Validate input before sending requests to avoid unnecessary API calls

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Getting help

If you encounter errors that are not documented here or need assistance:
  1. Review the endpoint-specific documentation
  2. Make sure you understood how Authentication works
  3. Contact lemlist support through the feedback form