This must be a stupid misconfiguration but I can't figure it out, perhaps somebody has a good idea. I have ISPConfig running on https://its.no-fun.de:8080. I want to configure port 80 as a portal for my clients, so I configured a site with domain "no-fun.de" and auto-subdomain "*.". Now this site can be accessed on port 80 with its main domain and all subdomains except http://its.no-fun.de. For instance, http://www.no-fun.de works fine. The error in the Apache log is: I have been searching for a dedicated setting of its.no-fun.de anywhere else, but I can't find any. For instance, when I grep -r its /etc/apache2, there is no result. When I configure an explicit subdomain 'its.no-fun.de', the situation does not change. The question is, why is subdomain 'its' handled in a special way? Anybody any idea? Forgot to mention that 'its.no-fun.de' is also the hostname of my server, which might be the core of the problem.