Guaranteeing the delivery order of multiple SMS/MMS messages is a challenging task when using Twilio's API. To solve this issue, developers can use one of three approaches: adding delays between messages to minimize the chances of them being delivered out of order, polling the message status over and over until it is delivered, or utilizing the status callback webhook. While these solutions are not foolproof, they provide a good starting point for ensuring that messages are delivered in the correct order. By implementing one of these approaches, developers can build more reliable applications that meet their specific requirements.