When attempting to add a user from a Windows domain to Portal for ArcGIS, the following error message is returned:
Error: One or more members are missing an email address and will not be added.
An email address is required when adding a user from a Windows domain.
Note: Note that this user does not have a single sign-on experience. This user is seen as a built-in user and must use login credentials to log in. It is recommended to add users with an email to be able to use the forgot password functionality.
Note: The following is an example of the Portal Administrator Directory URL: https://portalurl/webadapter/portaladmin.
Note: Check existing users to see how the organization's usernames are displayed in Portal for ArcGIS. The following is an example of a Windows domain name: domainname\username or username@DOMAINNAME
Note: The following is an example of a test email address: email@example.com.