I perhaps didn't explained it right - I tried to install ISPConfig, but installation failed. Then, I uninstaled ISPConfig and deleted what left and installed webmin+virtualmin. Because some settings still was left from ISP, I removed postfix (yum remove postfix) and then build postfix 2.9.4 from source as root.
Unfortunately, server gone live, web site must be running so some switch to ISPconfig is not a option now. Is there some own postfix solution to rebuild settings, or something in webmin/virtualmin?