I have Azure Windows VMs that will require some users to connect to Office 365 for email and OneDrive uploads and downloads.
Is my business's Office 365 considered an Azure service?
Will the traffic leaving my VMs stay within Microsoft's network, or Azure backbone, instead of going out into the public Internet?
If it stays within Microsoft's network, does it incur the regular egress network charges leaving my VNet?
In Microsoft's Doc for virtual networks their statement reads:
Internet: Routes traffic specified by the address prefix to the Internet. ...If the destination address is for one of Azure's services, Azure routes the traffic directly to the service over Azure's backbone network, rather than routing the traffic to the Internet. Traffic between Azure services doesn't traverse the Internet, regardless of which Azure region the virtual network exists in