A: With an Exchange 2003 installation, the Active Directory (AD) DNS name can be changed. However, this is not allowed for Exchange 2007 or Exchange 2010.
No version of Exchange supports the changing of a domain’s NetBIOS name. If you need to perform an AD rename with Exchange 2010 installed, you would need to create a new AD forest, install Exchange 2010 into that new forest, and migrate all the objects over, which is a huge undertaking.
Remember that if you only need email to support a different domain name (e.g., the @domain.com part), you can just modify the Exchange policies and configuration to support alternate SMTP aliases and change the default SMTP domain. You don't need to change the AD domain name!