Thanks to Bink for this... Download Exchange 2003 RC1 to get the stability and quality you need to start planning your Exchange 2003 deployments. Exchange 2003 RC1 is a 120-day evaluation edition that can be directly upgraded to the released version and released 120-day evaluation code. You can upgrade from Exchange 2003 RC1 to the released version of Exchange 2003 by performing in-place upgrades.
The Exchange 2003 RC1 program is designed to give you an opportunity to try the new and enhanced features for 120 days. To experience the full functionality, deploy Exchange 2003 RC1 in a test operating environment running the released version of Microsoft Windows Server™ 2003. Exchange 2003 RC1 also runs on Windows 2000 Server with Service Pack 3.