As part of the periodic renewal cycle, the Azure IoT Hub leaf certificates used for TLS connection will be renewed starting mid-May 2017. This could potentially impact some clients connecting to the Azure IoT Hub service. This change only impacts Azure IoT Hubs created in public Azure cloud, and not Azure in China nor Azure Germany.
We recommend validation to mitigate any untoward impact to your IoT infrastructure connecting to Azure IoT Hub. We have setup a test environment for your convenience to try out before we renew the leaf certificate in Azure IoT Hub.
Learn about it on the Azure blog.