I used to be an IT infrastructure person. I selected and installed the first Microsoft Exchange mail system in the large company I was working in during the mid 1990’s. I championed and introduced VMware as the virtualisation platform of choice in a different job in the mid 2000’s, before moving on to a technology innovation role to identify and champion new technologies.
If I was working in a company now in an infrastructure role I would have as much as possible of the server infrastructure off premise in the public cloud. I’d only have servers on premise, or in private cloud or a 3rd party data centre, if the data was too sensitive for a public cloud service. And in that scenario I’d adopt a hybrid cloud model with all the data I could have out on public cloud servers, with just the sensitive data on the in house part of the hybrid cloud. The public cloud services I’d use would be Office 365, Microsoft Azure, maybe Igloo for Intranet services, Slack for messaging, and Airwatch for endpoint device management. If any email accounts were mission critical I’d put them on the lowest spec Exchange Server possible in house as part of a hybrid deployment of Office 365.
The IT budget I controlled would be spent on having good redundant Internet connections and giving the users the choice of device they want to use. Be it Mac, Windows PC, iOS or Android tablet, iPhone, or Android phone.