I noticed someone asked about Multiple Domains but I am more interested in Multiple Organization Units, although I will admit that I am not an Active Directory expert.
Basically, under the tab - USER - there is a user-specific setting for "Account Suffix" and it only allows you to enter in one. So for example, I might have americas.company.com but I also have emea.company.com and asiapacific.company.com...
So is there a way to check the username against other organization units? That way if the user is part of a single domain but instead part of a different organization unit and have this appended in the following option. If we so choose...
Alternate Conversation:
Multiple Domains
http://wordpress.org/extend/plugins/active-directory-integration/