Submitted to the faculty of the School of Informatics in partial fulfillment of the requirements for the degree Master of Sciences in the School of Informatics,Indiana University May 2005 / An email overload problem occurs when users try to utilize email service in a way it was not designed for. Moreover, many web-based email services provide large email storage space and users tend to keep more unused emails. Issues that cause email overload are 1) Keeping too many emails, 2) Using email for conversational threads, and 3) Using email as a task management tool. Forty-five participants were selected to participate in user study sessions including questionnaire, time-on-task study, and interview. Participants were divided into three groups of 15. Participants in the first group were assigned as Gmail users. Participants in the second group were assigned as Yahoo! Mail users. After finishing user study sessions for the first two groups, the results were analyzed and the new web-based email prototype was designed as a suggestion of how the web-based email could be developed to handle the email overload problem. Then users in the third group tested the new prototype in the same manner the research was conducted with the first two groups of users. Users in the third group were satisfied with the features and design of the new prototype. The design of the new prototype focused on solutions that are able to handle email overload problem which are 1) Email categorizing, 2) Email thread grouping, 3) Email searching, and 4) Email task management. This study illustrates how the web-based email can be designed with features to handle email overload problems while maintaining the interface usable to most users.