No I didn't had to remove the .htaccess file.
I created a sym link to my roundcube folder which is on my debian server at /usr/share/webmail/
I'm at the moment not at home and I will look for a solution as soon I'm at home. Should be tomorrow.
PS: I Use FastCGI php for my server and try to change the ip of the domain to a xxx.xxx.xxx.xxx or to *. ISPConfig seems to have here problems. Maybe that helps.
Last edited by Horfic; 15th April 2009 at 12:54.