Hi Jazer,
By default, Outlook 2016 should be able to connect to Exchange 2010.
How many users are affected by this issue currently? Are these users using external clients or internal clients?
If you haven't tested Outlook anywhere function on internal clients, please also have a try with it and let us know the result.
Besides, please also try testing the connectivity via the Remote Connectivity Analyzer tool and see whether there is any error. If any, could you please provide the result to us so that we can further look into it?
Regards,
Steve Fan
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