UPN not picked up in logon

hi,

 

im struggling a bit with an exchange2016 implementation on APM. As it stands today, if a user types in email address as username, the logon will fail. domain/username seems to be working fine, but the customer would like both options available, at least for a time, where email address should eventually become the only username available..

 

Does anyone here have any experience with this, and could offer some insight?