This article will show you how to configure Exchange Server 2016 Integrated Windows Authentication which will not ask for a user name and password when using OWA.
With Exchange Server 2010 Integrated Authentication required that CAS server will be the only role Installed on the server, Since CAS server role does not exist on Exchange Server 2016 the old requirement Is obsolete.
To configure the feature Open ECP -> Virtual Directories -> Select the server from the picker and select OWA
Go the Authentication and set your settings as the screenshot below.
Do the same for the ECP directory
Restart IIS using iisreset /noforce
Next time you log In you will logged In automatically