Set up a Monit monitoring service for your websites and services. Monit is a free and open source service monitoring application which can perform various event-based actions. Monit can send email notifications, restart a service or application, or take other responsive actions. We set Monit up on a Ubuntu 14.04 VM, built on Hyper-V. And we use Monit to monitor several websites, and send out notifications on downtime.
Delete all MAILER-DAEMON emails from your Postfix queue fast when it matches a sender or recipient email address condition. For example, delete emails based on Message-ID header, To or From address.