There are about 668 mln email users worldwide, with over 1.2 bln active email accounts, The Radicati Group says. Worldwide email traffic per day totals about 135 bln messages, of which 67% are spam. Approximately 65% of worldwide email mailboxes are delivered through a webmail service provider or ISP. Mobile phone mailboxes currently account for only 2% of worldwide active mailboxes. The email archiving market is expected to double in size annually over the next four years, and revenue in the wireless e-mail market is expected to increase by over 300% by 2009. Revenue in the Instant Messaging market will increase at an average annual rate of 27% over the next four years. In the messaging software market, revenue will increase at a steady average annual rate of 9% between 2005 and 2009.