thank you very much. the problem had been solved!!!!
I have removed ISPconfig and postfix rpm. then install step 12 of the perfect server manual again.
that was because the first time I had installed ISPconfig 3 and then removed it and installed ISPcnfig 2. but the configuration in /etc/postfix/mysql-virtual_* was remained.
I think the ISPconfig does not completely uninstalled by removing /root/ispconfig and /home/admispconfig !!!