Suppose you want to maintain the temperature of the machine. If the temperature of the machine goes beyond 50 degree Celsius, you want to be notified by e-mail. This exercise can be part of your home automation. An Internet connection is essential for this exercise. Your router to which you connected BeagleBone should have some kind of working Internet connection via fiber, WAN port, DSL RJ11, or GSM dongle.
sudo npm install –g nodemailer
The source code and other information can be found here: https://github.com/nodemailer/nodemailer.