Originally Posted by farao
I'm not entirely sure which postfix you need to edit, since I believe ISPConfig installs its own postfix, but I would assume you need to edit the files in the ispconfig subfolders. Please correct me if I'm wrong.
No, ISPConfig doesn't install it's own postfix, it relies on the postfix that's already on the system. The postfix files should then be under /etc/postfix/.