Using the Manila sub-menu of the Tools menu where the docs call for using the Server menu.
user.prefs.mailaddress must not be empty
The Open Admin Site command opens http://127.0.0.1:5337/ and this doesn't work. Probably because we've got a different default setup for responders, which is totally cool.
So I tried going to opening the control panel instead and that worked.
Here's a screen shot of the home page of the control panel site.
The discussion on this should continue on the Frontier-user list.
