jbrodkin writes "An open-source, cloud-based e-mail alternative to Microsoft Exchange called Open-Xchange has signed up two new service providers and predicts it will have 40 million users by the end of 2011. Based in Germany, Open-Xchange has tripled its user base from 8 million to 24 million paid seats since 2008, with the help of three dozen service providers including 1&1 Internet, among the world's largest Web hosting companies. Microsoft is still the 800-pound gorilla, with a worldwide install base of 301 million mailboxes in 2010, expected to reach 470 million by 2014. But Open-Xchange is luring numerous service providers who are wary of Microsoft's attempts to compete against its own partners by selling hosted e-mail services directly to its customers."
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