You need to set GroupWise as the default mail client in KDE and Gnome, for Linux.
1. In KDE, go to KDE Control Center > KDE Components > Component chooser > Email Client.
1a. Check off "use different email client" and enter "Groupwise" in the field, since the gw client should be in the path already. Or, you can put in the full link as "/opt/novell/groupwise/client/bin/groupwise". Mailto links should now work from KDE.
2. In Gnome, go to Control Center > Preferred Applications > Internet.
2a. From here, select the dropdown under "mail reader" and select Custom, which lets you edit the field.
2b. In the field, enter either just "groupwise %s", or the full path: "/opt/novell/groupwise/client/bin/groupwise %s"
This solution was tested on OpenSUSE 10.3 but should work on any recent SUSE OS, from NLD9+.