Microsoft started testing on Monday a new computer server software that allows corporate customers to make Web-based phone calls through its Office suite of business software.

Microsoft Office Communications Server 2007, due for release in the April-June quarter of 2007, will push the software giant into the business telephone market at a time when many large companies shift to cheaper telecommunications powered by Voice over Internet Protocol (VoIP) technology.

Ahead of the official release, Microsoft said it will make the technology available to 2,500 companies for testing.

The new voice server will allow users to instantly call anyone from within Office applications by clicking on a person's name and initiating a call.

For example, a worker who receives an e-mail in Office Outlook from various colleagues can simply click on each colleague's name to check their availability and place a person-to-person phone call or arrange a conference call.

The company's push into the business telephone market pits Microsoft against Cisco, IBM and other technology companies seeking to cash in on growing demand for VoIP.

Microsoft Chief Executive Steve Ballmer has predicted that within 10 years all business communications will be Web-based, meaning hundreds of millions of people will change how they communicate.