How To Relay Postfix mails via smtp.gmail.com on Ubuntu 14.04.1 – RunAbove knowledge base https://community.runabove.com/kb/en/instances/how-to-relay-postfix-mails-via-smtp.gmail.com-on-ubuntu-14.04.html
Postfix: Configuring Gmail as Relay – matthew hawthorne is mhawthorne.net http://mhawthorne.net/posts/postfix-configuring-gmail-as-relay.html
12.04 – How can I configure Postfix to send all email through my Gmail account? – Ask Ubuntu http://askubuntu.com/questions/228938/how-can-i-configure-postfix-to-send-all-email-through-my-gmail-account
Configure Postfix to Use Gmail SMTP on Ubuntu – EasyEngine https://easyengine.io/tutorials/linux/ubuntu-postfix-gmail-smtp/