Once we prep the Forest and Domain for 2010, there is a warning displayed about how this will prevent any additional Exchange 2003 servers from being installed in the Org. However, what if there was a DR scenario? Could we reinstall an existing Exchange 2003 server using the /DisasterRecovery switch?

If this environment is only Exchange 2010, then the answer is no. Please take a look: http://mcpmag.com/articles/2010/07/19/exchange-2003-or-2007-in-2010-environment.aspx.

Yes,"You can only install additional Exchange 2003 servers in your organization if an Exchange 2003 server was there when the first Exchange 2010 server was installed. " Exchange 2003 - Planning Roadmap for Upgrade and Coexistence http://technet.microsoft.com/en-us/library/aa998186.aspx If you decommissioned all your Exchange 2003 servers, then want to recover an Exchange 2003 server in your Exchange 2010 organization, I think it is also unsupported. Frank Wang TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Vegas588, Any updates?Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Thanks Mr. Wang!