When trying to set forwarding, the process fails and error is found in the log:
15:47:02 ERROR: [1298-11-2-00000000] The program launched to migrate user 'username' aborted.
GroupWise Post Office may have a minimum client release version specified that is higher than the one configured on the Migration Console. For example, if the minimum client version is set to 6.5.7, all other versions lower than that will be locked out (regardless of your admin credentials)
1. Browse to the Post Office where the user mailboxes reside
2. Right click | Properties
3. On the GroupWise tab, select Client Access Settings
4. Verify / set the Minimum Client Release Version (x.x.x) to a version LOWER than what is on the Migration console.