Here's a question, in an existing active directory forest (one root domain and three child domains) can I add an UPN suffix in domains and trusts and then change all the user logins to that new suffix. For example, the root domain is ts3d.lan and the child domains are uk.ts3d.lan, bend.ts3d.lan and lyon.ts3d.lan. Our email domain is techsoft3d.com. All emails address are unique and are the same as the user name (minus the domain name)
So if I made this change, and then changed the accounts in each AD domain e.g eric@ts3d.lan to eric@techsoft3d.com this should work f I have my thinking right.
working by having people able to login to their domain attached computer with foo@techsoft3d.com and working that people can use foo@techsoft3d.com as their account when login into Exchange.