Co-existence between BPOS communicator and on premise exchange

Office Communications Online integration with on-premises Exchange Server 2007

Office Communications Online will integrate with an on-premise server running Microsoft Exchange Server 2007. Office Communicator will display presence updates and Out-of-Office information from the on-premises Exchange server. Office Communicator will communicate with your on-premises Exchange server using its external Exchange Web Service (EWS) URLs. For more information about EWS URLs, see How to Configure an External Host Name for Outlook Anywhere.

For more information on EWS click here

Microsoft Online Services release notes