I had Windows 2000 Active Directory domain with member server running Exchange 5.5. I needed to install new member server with Exchange 2003. I have upgraded Active Directory server from Win2k to Windows 2003. I have installed Exchange 2003 co-existing with Exchange 5.5. Active Directory is not being synchronized with Exchange 2003 Server. When I create a new user on AD, it does not ask to create a mailbox for the user. Moreover if I create a user on the Exchange 2003 server, that user is not found in Active Directory server. Seems to be Synchronization problem. Likewise I can not move mailboxes from Exchange 5.5 to Exchange 2003 server. Any help ... will be appreciated.