Fails to publish with user-defined topic to IoT hub

Hi all,

I am new to azure ecosystem. I followed some examples and documents and able to connect to the Azure IoT Hub and able to send data. The data is being sent on device/<deviceID>/messages/events topic(telemetry message) topic. From same application, I am not able to publish the message on custom topic(user-defined). Can you please help me if I am missing any additional configuration/settings for Azure IoT?