The Exchange Server Deployment Assistant has now been enhanced to include support for configuring rich coexistence for organizations interested in maintaining some users on-premises with Exchange 2007 and some users hosted by Microsoft Office 365 Beta for enterprises in the cloud, announced Microsoft today.
This scenario is in addition to the existing support for configuring rich coexistence between on-premises Exchange 2003 organizations and Office 365 Beta. The coexistence information is only available in English at this time and additional rich coexistence support for Exchange 2010 will be added the Deployment Assistant soon.
"If you're not already familiar with the Deployment Assistant, it allows you to create Exchange Server 2010 on-premises configuration and deployment instructions that are customized to your environment. It asks you a small set of simple questions and it provides a checklist with instructions that are designed to deploy or configure Exchange 2010 based on your answers. In addition to the online checklist, you can even print a PDF of your checklist."
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. This approach is different than the simple exchange migration ("cutover migration") and staged Exchange migration options currently offered by Office 365 Beta outlined in E-Mail Migration Overview.
More Info: Exchange Server Deployment Assistant
[Source: Exchange Team Blog]