Here’s one of the major reasons. Many marketers miss out on sending the email campaign the right way. Did you know that you should not be sending an email campaign at one go, to many thousands of recipients? Well, if you send such an email, you're likely to lose a few subscribers as your message isn't targeted. You'll end up straining your message server, thereby affecting your email's deliverability. In addition, you might miss out on getting an overall understanding of your campaign's performance. 

This is where ‘smart’ email marketing comes into picture. By segmenting your mailing lists based on specific criteria, you can understand your audience better and send emails catering to each of them. You can divide your emails based on segments, which helps you analyze your performance results and get a clarity on the real-time campaign metrics.