Email is one of the most widely-used means of communication, as evidenced by the soaring rates rates of mailing volumes since the introduction of email as an Internet service. While considerable work has been done in improving the efficiency of email management, there is a need for improving its functionality (effectiveness). Typically, users are given few means to intelligently explore the wealth of cumulated information in their email archives. We address these shortcomings by designing Information Visualization tools for email data. We have devised the MailExplorer system which aims at enabling the user to explore large quantities of email data, reflecting the rich meta data and content stored in email collections. The system allows its users to visually analyze temporal and spatial distribution properties, as well as content-based characteristics in their email archives.