I will answer myself
in case anyone else has the same problem with a leased server:
1. in /etc/sysconfig/network set the hostname:
2. In /etc/hosts set the ip with your new hostname
127.0.0.1 localhost.localdomain localhost
You do not need to change anything else in ispconfig, postfix, etc, all should come together on the reboot. Now the mail uses server.wvisw.net for hostname and spamassassin is happy and no loops and everything seems right.