Make sure that you have a co-domain mydomain.com with empty hostname field in the website www.mydomain.com.
I have that enty in ispconfig settings, but i cant access it, i got 3 External DNS servers, but how do i configure a record without www ore someting else?
If you use the ispconfig DNS manager, the records are created automatically. As you seem to use another software, create it manually like this: domain.com. IN A IP3