The design of the GroupWise 8 client requires that external user's free busy data is queried through a "Free/Busy URL". This means the a GroupWise 8 client workstation will need to be able to access the CMG server hosting the ExchangeFreeBusyService on port 80 or port 443, depending on the configuration of the CMG Directory Connector Service Settings.
STATUS
An Enhancement Request, TFS 380126, has been logged to add this GroupWise 8 client requirement to the list of the Coexistence Manager for GroupWise (CMG) port assignments in the documentation.