When running option GroupWise Administrative Function in Administrative Driven Batch Migrator, the forward is not being added to the properties of users the in Exchange(proxyAddress).
Quest GroupWise Migrator does not make those changes in Exchange. It basically creates the forwarding rule within GroupWise.
Either manually, via script or policy, make sure that in your Exchange server, the mailboxes that are being processed are ready to receive email for the target email address (for example firstname.lastname@example.org). This can be done via setting the proxyAddress.