A move to Office 365 means organizations must access some mission-critical services over the Internet. This isn’t often a major issue, and any downsides are outweighed by the benefits of consuming cloud services instead of managing services on premises.
Some organizations have a complex infrastructure and established regional and worldwide networks; they want to retain the same level of traffic management and reliability they’re accustomed to when they migrate to Office 365.
Microsoft Azure ExpressRoute connects to Office 365 and is used when you need a high quality of service. Azure’s infrastructure as a service offering allows companies to directly connect their organization’s wide area network (WAN) to Microsoft’s infrastructure, rather than connecting across the Internet. The feature taps into Microsoft Edge nodes located across the globe via its multiprotocol label switching (MPLS) network. It’s as close as you can get to having Office 365 on your network.