Here is a list of build numbers for Exchange 2000/2003:

Exchange 2000:

* 4417.5 = Exchange 2000 RTM

* 4712.7 = Exchange 2000 SP1

* 5762.4 = Exchange 2000 SP2

* 6249.4 = Exchange 2000 SP3

* 6396.1 = Exchange 2000 Post-SP3 Super Roll-up

* 63xx/64xx = Exchange 2000 Post-SP3 Hotfixes

Exchange 2003:

* 6728.12 = Exchange 2003 Beta 1

* 6803.8 = Exchange 2003 Beta 2

* 6851.10 = Exchange 2003 Release Candidate 0

* 6895.5 = Exchange 2003 Release Candidate 1 (Candidate)