Microsoft Wednesday sent Exchange 2010 out into public beta. It’s its first server built from the ground up, according to Microsoft, to be deployed in the cloud as an online service as well as on-site.

Microsoft expects to start selling the thing in the second half. It will be available as a cloud service from both Microsoft and third parties. Microsoft also conceives of it being available as a hybrid: a mix of both the cloud and on-site.

What it will cost as an online service is still a mystery. Microsoft already has a hosted version of Exchange, Exchange Online, based on Exchange 2007 that users will eventually be able to upgrade to Exchange 2010.

Microsoft also said it expects Office 2010, SharePoint Server 2010, Visio 2010 and Project 2010 to go into technical preview in Q3, ahead of release to manufacturing sometime in the first half of next year.

Office 2010, which was code named Office 14 and has now been officially christened, is supposed to include versions of Word, Excel, PowerPoint and OneNote that take on Google Apps and other web-based productivity interlopers.

There’s supposed to be a free ad-supported version of the widgetry and an ad-free paid version. The un-free Google Apps Premier Edition runs $50 a seat a year.

The beta Exchange has some new features. For instance, it can now run on lower-cost direct-attached storage, a change that Microsoft calculates could save users up to 85% on their storage costs.

It also introduces an integrated e-mail archive for compliance and e-discovery purposes and warns users before they send mail to large groups or outside the organization, a feature that could protect against information leaks.

Users can also remove themselves from an irrelevant e-mail string by hitting an e-mail “mute button.” And Exchange 2010 can transcribe voice mail.

The widgetry supports Safari and Firefox as well as Internet Explorer, but it only runs on Windows Server 2008.

See www.microsoft.com/exchange/2010 for the beta.