Microsoft has updated the ESDA (Exchange Server Deployment Assistant) to include support for rich-coexistence scenario between On Premise Exchange Server 2010 and Office 365.
This scenario was missing since the begin of the Office 365 beta (only coexistence with Exchange 2003 and 2007 was provided).
Rich coexistence (“hybrid deployment”) offers organizations the ability to extend the feature-rich experience and administrative control they have with their existing on-premises Microsoft Exchange organization to the cloud. It provides the seamless look and feel of a single Exchange organization between an on-premises organization and a cloud-based organization. In addition, coexistence can serve as an intermediate step to moving completely to a cloud-based Exchange organization.
Go to http://technet.microsoft.com/en-us/exdeploy2010/ for use
