4001: Delivery failed

Message could not be delivered. This may be due to an unreachable recipient or service disruption. This is an HTTP 500 error.

When reason is “Message delivery failed” (as opposed to “Message send failed”), a message.delivered webhook for the same message ID may still arrive later in some cases. This isn’t guaranteed, and we don’t have more specifics on this right now.

• Try sending the message again
• If the problem persists, contact support with the trace_id from the error response

• Sending messages
• Debugging