Originally Posted by kendel
Ok I see so they are defaulted, just wanted to be sure, so I installed roundcube on the mail server which responds to internal ip of 192.168.0.10/roundcube but it doesnt respond to the hostname of mail.example.com
All you have to do is to create a alias in apache for this type of access like I described in the PM and tahunasky explained in detail in his post. The setup is described in the perfect setup guide for squirrelmail and the setup for roundcube is similar, you just change the paths from squirrelmail to roundcube.
E.g. for debian, chapter 20.2: