The second reason that e-mail is so popular is because it is cheap. It costs nothing more than your time. No paper expense, no postage, no envelope expense.

• 电子邮箱之所以流行的第二个原因是它廉价。它不需要你投资一分钱,需要投资的仅仅是你的时间,没有纸张、投递和信封的开销。