In order to see that in your Control Center, you have to use package management to install the Wizards... however, the wizard for Postfix doesn't do a whole lot
-- You're better off using webmin (Install it with "Install Packages" if it's not already installed). How to know if it's installed: visit
https://your.server.here:10000 <-- Note the "s" webmin runs SSL by default on Mandrake 9.0