Among others, CNet is carrying this story. There's a great deal of additional material at their site, including this interesting architecture diagram. Is this a credible threat? Not yet. These guys have literally millions of man-hours of catchup to do before producing a product that does what Exchange and SharePoint Portal Server (their apparent targets) can do. I won't even attempt to list the hundreds of features that have to be implemented before they even reach parity with Exchange 5.5, much less Exchange 2000... much less Exchange 2003. Of course, since they're not trying to implement a mail engine they get off the hook for a lot of stuff. We'll see.