I'm running Zimbra 5.0 OSS edition. On the standard user login screen, "Mobile" is given as one of the choices, but selecting it just causes the standard AJAX client to load. Manually appending ?client=mobile works fine.
This happens from the two Nokia mobile devices we've tested, and from Firefox (haven't tested any other browsers/platforms).
Other people haven't mentioned this problem so hopefully I'm doing something wrong. Is there a setting I've missed? I haven't spotted any relevant settings in the admin panel.