I currently have an old Windows Server 2003 R2 domain controller, as well as a second server running Windows Server 2003 R2 64-bit hosting Exchange Server 2007. I have finally convinced the customer that it is time to migrate to a new server hardware and software environment. I have plenty of documentation on the Active Directory migration from 2003 R2 to 2012 R2, and it seems pretty straight-forward (with any "gotchas" accounted for). However, the existing Exchange 2007 server in the mix is troubling. I'd like to upgrade that to Exchange 2013 on a 2012 virtual guest machine, but I'm not sure of the order of migration, or if Exchange 2007 will have to exist for a short time in a 2012 environment before being migrated to Exchange 2013 on a new server. There is also the possibility that the customer will need to hold off on the Exchange portion of the migration/upgrade for several months, which will necessitate running Exchange 2007 on the same server after the 2012 R2 domain controller migration.
Are these two scenarios even possible "compatibility-wise", and if so, what are the migration steps? Any help folks can give me would be greatly appreciated!