Microsoft, if nothing else, has become a problem for Yahoo’s $350 million Zimbra acquisition and Google’s rudimentary Sites contribution to the advance of software-as-a-service announced last week by throwing open the more sophisticated Exchange Online and SharePoint Online to any business anywhere that wants to use the software as a service.

Last September Microsoft started offering the hosted versions of its Exchange Server and SharePoint Server to companies with 5,000 users or more. Now it’s making the stuff available to Joe’s one man shop down the street.

The new online services are available initially as a limited beta open to US companies that Microsoft says will become generally available in the second half. (See www.mosbeta.com to sign up.)

The offering covers e-mail and calendaring, like Zimbra and some of the other Google Apps, come to think of it, as well contacts, shared workspaces, web conferencing and videoconferencing. The stuff is supposed to be exactly the same online as it is when it’s installed locally.

Microsoft says the services can be deployed as a per-user subscription managed from Microsoft’s own servers, the company’s own servers or a combination of both. And it has altered its licensing accordingly although it has yet to disclose exactly how much a subscription will run.

It did however say that large customers on its Software Assurance plan with Client Access Licenses (CALs) could get the subscriptions at a discount and that customers with a subscription had rights to both the so-called Microsoft Online Services and on-premises server software so they can blend the two approaches.

It also said that at some point it would offer Exchange Online and SharePoint Online together with Office Communications Online and Office Live Meeting as a suite of services as well as separately.

A beta of Communications Online is due out before the end of June, with a final version coming next year.

Unlike Google, at least, Microsoft’s proposition doesn’t cut out the administrator, which may be of some comfort to the enterprise. IT can still monitor service performance; add and configure users; track support requests; and manage users and licenses. Google’s newfangled SharePoint-aimed Sites would dump that sort of thing on the ash heap of history.

Microsoft customers include Autodesk, Blockbuster, Ceridian, Coca-Cola Enterprises, Energizer Holdings and Ingersoll-Rand. Meanwhile, folks like Unisys, BT and HCL Technologies say they’re going to resell, customize, and provide consulting, migration and managed services for the stuff.

The announcement was made at this week’s Office SharePoint Server 2007 Conference where Microsoft said 100 million SharePoint licenses have been sold, breaking through the $1 billion milestone this year.

Microsoft also announced the general availability of its Search Server 2008 Express, the free, downloadable intraenterprise search product that targets Google’s Search appliance as well as a Silverlight Blueprint for SharePoint for customers who want to build Microsoft’s idea of rich Internet Applications (RIAs) based on SharePoint.

The Silverlight technology includes sample applications that combine Silverlight and SharePoint; best practices; and rich business data visualization and interactivity. See http://go.Microsoft.com/