Enterprises or partners can customize the user experience by writing "Web parts" and linking them to the applications, Elop said. For example, Microsoft demonstrated a Web part accessible through SharePoint Online that showed a sales team's progress against its objectives. That component was written in Silverlight and pulled up-to-date information from a database. Microsoft has opened up some APIs (application programming interfaces) to let enterprises or partners link up their own cloud-based services with hosted SharePoint and Exchange, Kelly said.

Partners voiced concern in March when Microsoft announced it would host applications itself, fearing they would end up in competition with the software giant. But with customization capabilities, partners have a better opportunity now to differentiate themselves, Kelly said. And if they don't have to deploy servers and other infrastructure at customers' premises, selling hosted software instead, the partners can draw in customers that might not have the capital today to buy those physical deployments, he added.

Another overture to partners is already a hit, Microsoft said. At its Worldwide Partner Conference in July, Microsoft announced a program under which partners can receive an ongoing annuity revenue stream for online services they sell. That comes on top of any revenue they earn for performing integration, migration and other services for their customers. Since that time, more than 1,500 partners have signed on to that program, Elop said. With Exchange Online and SharePoint Online now available to all sizes of businesses through partners, they can now begin to reap the benefits of the program, he said.