Can I use IWA authentication to access Portal for ArcGIS without using the ArcGIS Web Adaptor?

Answer

It is possible to log in to Portal for ArcGIS using Integrated Windows Authentication (IWA) log-in credentials, without going through the ArcGIS Web Adaptor.

IIS normally performs an initial authentication step, and forwards the log-in information to Portal. The Web Adaptor passes the log-in username to Portal in the format username@DOMAIN. Logging in directly to Portal is possible by changing the usual user login domain\username to the format username@DOMAIN (note that the domain part must be in capital letters). The usual Windows password is used.