Unfortunately, Mac OS X Server’s Server Admin is far from being perfect. Especially when it comes to mail, web and name server services. If you happen to modify Postfix settings from the command line, while keeping Server Admin open, it can happen that whatever changes you have made will be overwritten and that any future changes you make in Server Admin do not take.
If this happens, close Server Admin, make a copy of
and delete it. When you re-open Server Admin it should read the settings from the configuration files.