As I'm learning English and collecting supporting arguments for different exam topics, so I would take advantage of the ideas to put it into English. I think your entry is perfect. It has topic sentence at the beginning which signals the readers what you are talking about. On top of that, the supporting arguments is closely linked to and fully elaborate the topic sentence. The reason why traditional postage is replaced by emails is because the latter one is on time and less time-consuming. If we rely on posting, it takes a couple of days for the recipients to receive the letters. What is worse, if the sender and recipient reside in different countries, it would take much longer for the delivery of the words. In contrary sending email saves the time and ensures the recipients can read the content on a timely basis. Furthermore, the in-advanced preparation of sending a letter by post is complex. For example, it is necessary to have letter paper and pen ready. When the letter is finished, we need to purchase stamps and seek for post box to get it sent. Based on the above factors, the number of people relying on traditional postage is decreasing dramatically.