All three services will go live at the same time in April.

Office Communications Online is built on Microsoft's Office Communications Server software, which provides instant messaging, presence and other collaboration features including VoIP and integration with corporate PBX technology.

However, Office Communications Online offers only a subset of the Office Communications software. "There is not feature parity with the on-premises version," Betz says."With online you get IM and presence. You can see presence in a chat session, but Office Communications Online is not integrated with the on-premises PBX."

The Office Communications Online dedicated version has the same limitations.

But Betz says the target customer is the same as with all Microsoft services -- those looking to save money.