This is the default example configuration of postfix provided by Postfix. This config file was generated by Postfix running on Debian 9.
It is located under: /etc/insserv.conf.d/postfix
$mail-transport-agent postfix
Download the raw file with wget or curl
wget -O postfix.example http://exampleconfig.com/static/raw/postfix/debian9/etc/insserv.conf.d/postfix
curl http://exampleconfig.com/static/raw/postfix/debian9/etc/insserv.conf.d/postfix > postfix.example
Other config files you might find useful