Exchange 2010 has been the most modular version of exchange that allows extensive security implementation and high availability. All newer version (Exchange 2013 to 2019) deviates from modularity and downgrade back to Exchange 2003. It appears the new CEO of Microsoft, Satya Nadella, has a different agenda that deviates from maintaining enterprise class products and solutions.
Almost every products and solutions driven by the Microsoft CEO lacks forward technology advancement. Instead, he wants to turn back the clock to the good old days of Microsoft Windows NT 4.0. Please be advised that O365 is a cut down platform of the On-Premise products and solutions that provides limited customization and integration and should only be applicable for businesses less than 500 On-Premise users.
High utilization of WAN bandwidth will cost your business as an end result, and there have been many complaints around this area that O365 was implemented without the completion of a business assessment. Businesses that were forced or blindly adopted O365 are faced with complexity of excess bandwidth utilization, limited integration, and limited flexibility. Out of fairness and honesty, some businesses have failed because of this. Today businesses are dynamic.
Azure and O365 are for business that does not have the intellectual property to maintain and/or manage their own datacenter. For medium and large enterprise class businesses, be very careful in planning, designing, and implementing any 2013 to 2019 application server products/solutions from Microsoft. Extensive analytics with capacity planning is required before migrating away from the 2010 series of Microsoft Application Server SET.
If your organization is driven by Microsoft Products and Solutions, please do not implement VMware as a virtual solution. Event logs in Microsoft Products and Solutions can isolate the exact failure. Failure caused by VMware will not be address by the VMware Corporation as VMware neglect to fix major bugs since 2008. Selection of hardware must be compliant to any virtualization technology.
Hope this helps!