To learn more about how you can check the status of sent message see the Messaging section of the corresponding SDK:
iOS SDK - Messaging | Chat | iOS SDK | QuickBlox
Android SDK - Messaging | Chat | Android SDK | QuickBlox
React Native SDK - Messaging | Chat | React Native SDK | QuickBlox
Flutter SDK - Messaging | Chat | Flutter SDK | QuickBlox
Feel free to check our official documentation for more information that will help you to integrate QuickBlox services into your applications / projects or contact our Support team by submitting a ticket if you have any other questions.