MS Exchange Server 2003 Question:

No, the property sheets of the 2003 servers will appear as read-only. You should avoid using Exchange 2000 ESM in environments where Exchange 2003 is installed. Not only will you not be able to access new Exchange 2003 features, but there is also the risk of damage to new objects that Exchange 2000 does not understand. If you must continue to use Exchange 2000 ESM, apply the latest Exchange 2000 SP3 roll-up to your Admin workstation(s) - http://microsoft.com/downloads/details.aspx?FamilyId=E247C80E-8AFA-4C2A-96B3-F46D1808C790&displaylang=en

The roll-up includes support for the msExchMinAdminVersion attribute (also known as ESM versioning). Essentially, each Exchange object in the AD is stamped with a minimum admin version. If ESM detects that the data value is greater than the version of ESM running, it will not allow edits to that object.