Outlook 2016 can't connect to Exchange 2010 server after updgrading to macOS 10.12.5
I am having the same issue - called Microsoft and they said it is a known issue with the latest 1701 builds of Outlook at this time. They are working on a patch but in the interim the only suggestion is to install an older copy.

The version that does appear to work is v15.30 of build 1701.

The last two versions of that build - v15.33 and v15.34 have the same issue.