Comment 17 for bug 56235

When you manually remove conffiles (anything in /etc) dpkg remembers that and assumes you don't want them when you reinstall the package. So what you report in your first comment is the package management system behaving as designed. dpkg purge followed by an install should restore the config files. So far you are not experiencing any postfix related bugs. If you do, please file them as new bugs unless you're sure you've got the same issue.