Its not.
Here is the list of affected Microsoft products:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-44228
Microsoft has not identified any exploitation of our enterprise services as a result of the Log4j vulnerability at this time. Our security teams have been analyzing our products and services to understand where Apache Log4j might be in use. As our investigation continues, if we identify any impact to our services or action required by customers, we will provide additional communications.