Introduction
To update your Reverse DNS record on a server hosted by Microsoft Azure, you'll have to utilize Azure's tools.
Procedure
We recommend you follow Azure's documentation to update your rDNS/PTR record, as it will always be the most up-to-date instructions for interacting with the Azure Cloud and their command-line software.
Resources
Please see "How to setup PTR (rDNS) records on your cPanel & WHM server" for instructions for other providers.