Sysadmin Geek posted a guide about setting up Email Alerts on Linux using Gmail or SMTP

Linux machines may require administrative intervention in countless ways, but without manually logging into them how would you know about it? Here's how to setup emails to get notified when your machines want some tender love and attention.
Of course, this technique is meant for real servers, but if you've got a Linux box sitting in your house acting as a home server, you can use it there as well. In fact, since many home ISPs block regular outbound email, you might find this technique a great way to ensure you still get administration emails, even from your home servers.

  How To Setup Email Alerts on Linux Using Gmail or SMTP