I’ve been asked this one a couple of times in the last few weeks as we continue to work on some GroupWise and other migrations.
To identify the Exchange schema level which is set for your forest you can navigate to:
CN=ms-Exch-Schema-Version-Pt,CN=Schema,CN=Configuration,DC=DN-of-forest-root-domaincontroller
In the Attribute Editor tab, scroll down to the “rangeUpper” attribute. If Exchange 2007 Service Pack 1 Beta 2 has extended the schema, the value should be 11116.
If you are using the RTM version of Exchange 2007 the value should be10637.
For Exchange 2003, the value should be 6870 and Exchange 2000 should return a value of 4397.