During the development of Essential Business Server (EBS), which deploys Exchange 2007 on a domain controller in a multiple domain controller environment, we faced a new set of challenges and developed resolutions for them. These resolutions can also be applied to any enterprise-level deployments with Exchange 2007 on a domain controller. One of the main challenges we faced in running Exchange 2007 on a Domain Controller was its recovery after a disaster. The recovery of Exchange when installed on a replica Domain Controller has a special formula that is quite different from any other topology. Exchange 2007 supports the /mode:RecoverServer that will automatically deploy the server binaries and recover all server settings from Active Directory, however, the Exchange computer object must be preserved and untouched in Active Directory for Exchange recovery to succeed.
Full Article: EBS Blog