⟩ How do I find an SMTP mail address in Active Directory if Active Directory Users and Computers tells me it is in use when I try to create a new user
Either open Outlook to create a new message with that SMTP address and hit “CTRL+K” to resolve it, or use a Windows Scripting Host script to find it. For the latter, see http://www.cdolive.net/download/adusermanagement.zip (look for FindUserWithADSI.wsf and FindUserWithCDO.wsf)