I think Microsoft might have something to worry about as Scalix gets a favorable review from InfoWorld. It looks like Scalix comes with all of the major capabilities of Exchange such as calendaring, email, etc. They also talk about a feature rich AJAX web client (Scalix Web Access aka SWA which sounds all too familiar to Outlook Web Access aka OWA).
Aside from the features, the price might also be right. It looks like Scalix only sells licensing by user (~$60 per user). Microsoft on the other hand requires licensing for the server software and then a client access license for each user. Purchasing Microsoft Exchange software and licensing alone can add up. However, I hear that Linux administrators are paid more than Windows Administrators so the cost of using either solution might balance out. But for some, just being able to use a Microsoft alternative is worth more than money.
I hope to give Scalix a shot in the summer, after I graduate from Grad school and have more free time!
