This following documentation from Microsoft outlines IP’s and URL’s that should be whitelisted.
In addition to what’s documented, whitelist the following IP’s:
The most important pieces from the linked article are :
IP addresses and range restrictions
Ensure the following IP addresses are allowed for outbound connection, so your organization works with any existing firewall or IP restrictions.
|IP V4 ranges||IP V6 ranges|
Ensure the following IP addresses are allowed for inbound connection, so your organization works with any existing firewall or IP restrictions.
|East United States||220.127.116.11/24|
|East 2 United States||18.104.22.168/23|
Other IP addresses
URLs to support sign in and licensing connections