The Radicati Group released <A HREF="http://www.radicati.com/">Market Numbers Summary Update, Q4 2003,</A> a new study showing year-end 2003 market share figures and four-year forecasts for all core market segments tracked by the Radicati Group. According to the study, there are 513 million email users worldwide, which send and receive over 57 billion email messages every day. In the enterprise messaging software market, Microsoft Exchange continues to lead the way with about 30% of the total installed base. IBM's Lotus Notes/Domino product follows closely behind with a 26% market share at year-end 2003. On the client side, Microsoft Outlook is by far the most widely used desktop client. Within the corporate market, Outlook has a 62% market share.