I have a custom skin set as default for all users/cos on my Zimbra Server (4.0.4 Network Edition).

Is there a way to change the default skin for the Server? I want a user who connects to the Zimbra webmailer for the first time, to see my custom skin login window. But although the default skin for the default cos is set to my custom skin, the login window is from the Sand skin (at least for the first time, the user connects to the server).