"In five years, 50 percent of our Exchange mailboxes will be Exchange Online," said [Microsoft exec Chris] Capossela, who expects a portion of Exchange Online customers to come from customers switching from International Business Machines' Lotus Domino system.

The company expects narrower margins as customers shift to cloud computing, although it sees opportunities for revenue growth.

Mary Jo: "Microsoft already is selling Microsoft-hosted versions of Exchange and SharePoint to large enterprises. In March, it started beta testing Microsoft-hosted versions of Exchange, SharePoint and Office Communications Server that will be sold to smaller companies, as well. The new subscription plans for those Microsoft-hosted offerings should be on the price list some time in the latter half of this year."

Nick Carr: "Capossela's assumption that Microsoft will be able to charge companies more under the cloud model seems optimistic, given the different economics of providing software as a web service and the aggressive pricing strategies of cloud pioneers like Google, Zoho, and Amazon."