Unfortunately, this means you can use email, but not the calendar. (In a slight twist of dramatic irony, we have had the same problem with Outlook 2016 trying

Unfortunately, this means you can use email, but not the calendar. (In a slight twist of dramatic irony, we have had the same problem with Outlook 2016 trying to talk to an Exchange 2007 server... ;-) Upgrading the server is on our TODO list for 2018, but for the moment, we have to live with it.)