Mail Servers Are Not DIY
Maintaining a mail server can take a lot of IT time, depending on the configuration. Spam filtering, server administration, even routine tasks like out-of-office are sometimes too clunky for an average user. And there will be down time. Local ISP issues, server overload, hardware issues. All can interfere with your business. Email is critical to your day-to-day operations. Business email in the cloud addresses all of these concerns. Office365 advertises 99.9% uptime, so far we have no reason to dispute this claim. There is also 24/7 support available in case of an issue (but call us first, talking to us is free).
Office Is Necessary
From the services that export XML spreadsheets which only Excel can read, to the vastly more extensive formatting options that render a native Excel spreadsheet incorrectly in Numbers, most of us will have to use Office at some point. There is no SAAS or traditional app which can replace all of the functions and features found in Office applications. With an Office365 subscription, Office Online is included. Go above the basic plan, and full copies of Office software and apps are included. And as long as you're subscribed, you never have to pay for an upgrade to a newer version.