Manual process of migration from GroupWise to Exchange will take a lot of time and also very risky. It may end with losing your data. To overcome these risk and to save time and money, I would like to refer Kernel for Novell GroupWise to Exchange migration tool.
This GroupWise to Exchange migration tool is a secure and reliable third party solution. The tool will provide users an easy-to-use and secure platform for quick and error free migration of GroupWise emails and other folders to MS Exchange server. To evaluate the features and functionalities, one can download its free trial version from http://www.groupwisetoexchange.net