Outlook mobile ActiveSync Autodiscover: connection with Exchange 2016

Hello, 

I'm facing with a annoying problem. Outlook mobile ask for email and domain\user just after get the exchange public domain. I presume "autodiscover" is ok (see photo.
Why only Oulook mobile ask for that? Gmail app and other works fine. I want that Outlook connects and ask only for password, like office 365. 

UPN is the same of the email