We have a bit of an issue. We are an internal MSP for a company that owns multiple companies. All 7 of these companies have their own forests/domains. Since we are migrating all of them to Office 365, we decided now would be the best time to collapse everything into one forest.
We have marked one of the domains as being the forest to be collapsed upon so we are adding the other 6's UPN suffixes to that one forest. We have created a 2-way Trans Trust between the collapsed domain and all of the other (hub and spoke, so to speak). We are then recreating the users on this domain and marking their suffixes as necessary, also granting and denying rights as necessary. This has been working great (surprisingly) since most of the domains were setup with non-routable domains (.local), however, we have one domain that is routable and the UPN suffix is not going away.
What will be the affect if we put the UPN suffix on the collapsed domain with the 2-way trust? I feel like it has the potential to cause issues, but at the same time, I'm not sure that it will. Just wanted to know if anyone else has had this scenario.