21609: Invalid 'StatusCallback'

This error occurs when the StatusCallback value in your Message request isn't a valid URL. Use a fully qualified public URL with a valid hostname. Keep the URL at 4000 characters or fewer.

• The StatusCallback value isn't a valid URL.
• The URL is longer than 4000 characters.
• The URL is missing part of a fully qualified address, such as the protocol, hostname, or path.
• The query string includes characters that aren't properly URL-encoded.
• The hostname is invalid. For example, it contains underscores.
• The endpoint isn't publicly reachable.

• Set StatusCallback to a fully qualified http:// or https:// URL.
• Use a valid hostname and remove unsupported characters such as underscores.
• Shorten the URL so it stays within the 4000-character limit.
• URL-encode query parameters before you submit the request.
• Make sure your endpoint is reachable from the public internet.
• Test with a temporary public webhook endpoint to confirm that Twilio can send callbacks. If that test succeeds, review your application logs, firewall rules, authentication requirements, and SSL configuration on your original endpoint.

• Messages resource
• Track the Message Status of Outbound Messages
• How to Test and Troubleshoot Twilio Messaging StatusCallback Failures