Internet portals have been using the email service to attract new members and to retain existing customers. This research aims to enhance the understanding of mechanisms associated to users' intention for email switching (IES). We have employed customer's satisfaction on email service, attractive alternatives, and switching cost to explain the dynamics of IES. Customer's satisfaction is measured in terms of storage capacity, spam blocking, interface design, and system stability variables. Setup cost and continuity cost are chosen as switching costs. By conducting a survey with 1,408 responses, we have found the vital importance of user satisfaction for service continuation. Variables of attractive alternatives and continuity cost demonstrated its strong association with IES. We have also found that attractive alternatives moderates the relationship of customers’ satisfaction and IES, but the moderating effects of switching cost are weak. Our investigation indicates that the findings of extant studies on the dynamics of service switching or re-purchase mostly apply to the email service as well.