We have a proxy for simple webmail systems such as roundcube. Its a tunnel, very useful to escape from routing issues that may arise.
What it does is very simple, for example proxy.ourwebmail.com listens on an IP and transmits to another IP, thus escaping from routing issue which could occur when user accesses the final Ip directly.
With GO this is hard because each customer has their own hostname, separate profile.
There really is no way to have a GO installation that works for any domain, witout specifyng them, etc?