When clicking on the "View" link included into the Quarantine Summary email notification (if configured as such), the Spam Quarantine does not show the User Preferences options (Bad and Good Senders). This way of accessing the quarantine is called "passive login" as the user does not need to enter any credentials nor type any address into the web browser.
The missing options are available when accessing the Quarantine "actively", this means to open the Spam Quarantine by pointing the web browser to the Control Center GUI and entering the credentials.
The issue has been solved in Symantec Messaging Gateway version 9.5.x.