Understanding Upgrade to Exchange 2010

Applies to: Exchange Server 2010 SP3, Exchange Server 2010 SP2

Microsoft Exchange Server 2010 can be deployed in an Active Directory forest that has an existing messaging system. You have a coexistence scenario if the following conditions are true:

• Exchange Server 2010 is deployed in an existing Exchange organization.

• More than one version of Microsoft Exchange provides messaging services to the organization.

You can't upgrade an existing Exchange 2000 organization directly to Exchange 2010. You must first upgrade the Exchange 2000 organization to either an Exchange 2003 or Exchange 2007 organization, and then you can upgrade the Exchange 2003 or Exchange 2007 organization to Exchange 2010. We recommend that you upgrade your organization from Exchange 2000 to Exchange 2003, and then upgrade from Exchange 2003 to Exchange 2010. For more information about upgrading from Exchange 2000, see Planning an Upgrade from Exchange 2000 and Upgrading to Exchange 2007.

When an organization gradually transitions a messaging system from Exchange Server 2003 or Exchange Server 2007 to Exchange 2010, the organization will probably have to maintain more than one version of Exchange during that time.

The following table lists the scenarios in which coexistence between Exchange 2010 and earlier versions of Exchange are supported.

Coexistence of Exchange 2010 and earlier versions of Exchange Server

The following topics provide information about upgrading your organization to Exchange 2010:

Understanding Upgrade from Exchange 2003 to Exchange 2010

Understanding Upgrade from Exchange 2007 to Exchange 2010

Understanding Upgrade from Exchange 2003 and Exchange 2007 to Exchange 2010

Also, see Exchange Server Deployment Assistant for information about a Web-based tool that can help you with your deployment.

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