Thanks Dan Ben-Amar for the heads up. Exchange 2000 Service Pack 3 (SP3) is a cumulative service pack that provides interoperability with Microsoft Windows® .NET Server Domain Controllers, fixes to customer-reported issues, and updates based on the Microsoft Trustworthy Computing Initiative. You should download and install Exchange 2000 Server SP3 on all servers running Exchange 2000.
Note: SP3 does not apply to Microsoft Exchange 2000 Conferencing Server. Download Exchange 2000 Conferencing Server Service Pack 2 (SP2) for the most recent Conferencing Server updates and enhancements.
Download: Microsoft Exchange 2000 SP3