Microsoft has announced that Exchange and Office SharePoint will be available as online subscription services for US customers from today, and for UK customers from spring next year.

"Today we bring business class communications and collaboration technologies to the cloud, and we are committed to delivering more capabilities in the months ahead," said Stephen Elop, Microsoft Business Division president.

Exchange Online and Office SharePoint Online will be available separately or as a suite together with Office Live Meeting for conferencing, Microsoft Exchange Hosted Services and Microsoft Office Communications Online for instant messaging and presence.

"No one has done what we are doing at this scale, and I am certain that our customers will continue to take on these solutions as our offerings grow," Elop said.

Peter King, Microsoft UK Office Server manager, explained that the new services will be unique because other leading email and calendaring subscription services are from consumer firms that have then developed business offerings.

Microsoft will also offer a choice of three Exchange and Office models: on-premise, pure cloud, or a mixture of the two, he said.

"Twelve to 18 months ago when software-as-a-service [SaaS] became a big buzz word we looked at the market and felt that pure-play delivery would not fit every customer in a long way," he said.

Microsoft UK Office marketing manager Gill Le Fevre said that Microsoft expects 50 per cent of its business customers to be using email via SaaS in five years' time.

UK customers that want to start trialling the new services should contact Microsoft's Partner Unit immediately, she added.

Le Fevre noted that this is the first suite of products that will sit on top of Microsoft's Azure platform for cloud-based computing unveiled at its Professional Developer Conference in Los Angeles last month.

"This platform will form the foundation for all Microsoft's cloud services," Le Fevre explained.

The Exchange and Office online services will be updated every six months, but customers can lag two updates behind the most current edition before they must upgrade, said King.

Microsoft also announced that it will soon offer another SaaS offering that will help IT managers secure and manage desktops.

These online services will be based on components from existing systems management, identity and security offerings, Microsoft said.