To construct AD Groups from excels

[sjorige]

Hello Team, 

We are planning to convert user access excels to ad groups.

1, We have a manual domain name GP which is managed using excel . can we move this to ad groups and create a new user directory connection

2,  Can we add users from other domains to US domain to US ad group and sync the user directory? Will that give access to the application?

3, How do we design a new domain in Active Directory