This is an important notification for customer managing access to internet (and cloud services) using Whitelist.
New Content Delivery Networks (CDN’s) are going to be used for managing Office 365 (and potentially Azure services) authentication.
If you are using whitelisting to allow Office 365/Azure services access to your end-user you have to be prepared ASAP.
The new CDN’s will be:
If you need the IP addresses you can go there https://endpoints.office.com/endpoints/worldwide
Remember there is no more RSS feed or web page listing all the IP address; you need to use the webservices as detailed here https://docs.microsoft.com/en-us/office365/enterprise/office-365-ip-web-service