Error schema

We use standard HTTP response codes for success and failure notifications, and our errors are further classified by type.


  • Status: 400
  • Message: We found an error with one or more fields in the request.
  • Suggested action: The message will contain more details about what field and error we found.


  • Status: 401
  • Message: Missing API key in the authorization header.
  • Suggested action: Include the following header in the request: Authorization: Bearer YOUR_API_KEY.


  • Status: 401
  • Message: This API key is restricted to only send emails.
  • Suggested action: Make sure the API key has Full access to perform actions other than sending emails.


  • Status: 404
  • Message: The requested endpoint does not exist.
  • Suggested action: Change your request URL to match a valid API endpoint.


  • Status: 422
  • Message: Attachment must have either a content or path.
  • Suggested action: Attachments must either have a content (strings, Buffer, or Stream contents) or path to a remote resource (better for larger attachments).


  • Status: 422
  • Message: The request body is missing one or more required fields.
  • Suggested action: Check the error message to see the list of missing fields.


  • Status: 429
  • Message: You have reached your daily email sending quota.
  • Suggested action: Upgrade your plan to remove the daily quota limit or wait until 24 hours have passed to continue sending.


  • Status: 429
  • Message: Too many requests. Please limit the number of requests per second. Or contact support to increase rate limit.
  • Suggested action: You should read the response headers and reduce the rate at which you request the API. This can be done by introducing a queue mechanism or reducing the number of concurrent requests per second. If you have specific requirements, contact support to request a rate increase.


  • Status: 451
  • Message: We may have found a security issue with the request.
  • Suggested action: The message will contain more details. Contact for more information.


  • Status: 500
  • Message: An unexpected error occurred.
  • Suggested action: Try the request again later. If the error does not resolve, check our status page for service updates.