This research paper tried to examine the effectiveness of email marketing on customer retention. The email is utilized to endorse the businesses it assists to create the association with the potential clients, keep the existing customers informed and please them by updating about the brands, offers, discounts etc., and motivate them for the client loyalty. Email marketing is an approach of utilizing email to get and to reach the target audiences. Email marketing is considered as an important tool for making leads to the firm where they utilize email as one of the important tool for endorsing their products and services. The business firms are utilizing email marketing as a customer retention tool. Email marketing will assist to reach an immense audience, generate brand awareness, customer engagement, and sell their products and services. Email marketing allows numerous clients to share valuable promotional space at less expensive. For all companies, they require to pay attention to their email marketing campaigns because email can be bounced by the readers. This research did a systematic review of advantages and importance of email marketing in the business world. The study suggests focusing more on high quality generic contents and the design of the email message. In addition, consistent with the viewpoint of studies in the field, the study confirms that customer engagement is an important predictor of consumer purchase, causing the conclusions that firm must spend in client engagement marketing initiatives to finally attain better performance.