I have a Windows NT 4 Domain that I am going to upgrade to 2000 Active Directory. I have Exchange 5.5 running on a BDC on this domain. My plan is to upgrade my NT PDC to 2000 AD and leave Exchange 5.5 running on an NT4 BDC for a few months before I actually upgrade it to Exchange 2000 on Windows 2000. Does anyone see a problem with this? Do you have any pointers or Microsoft KBs that could keep me from overlooking anything. Thank you in advance for your time.