We have a domain that spans several different physical locations with a few hundred users and client machines. We were set to upgrade our Exchange 2003 server to Exchange 2010 when we learned we could not move forward as scheduled because the domain name was not acceptable to Exchange 2010 because it contains an underscore, such as DOMAIN_1 (this was set up by a previous IT staff and we wanted to change it at some point.)
Instead of delaying the project and creating a lot of chaos by trying to rename the entire domain in a hurry, we came up with the following idea: create a new domain controller for the new domain name we want to use (DOMAIN2) and set up two-way trusts between DOMAIN2 and DOMAIN_1. Then we can build the new Exchange 2010 server on a member server in DOMAIN2, import the mailboxes from the exchange server on DOMAIN_1. If users can authenticate across both domains, I think this should work.
Can anyone think of any reasons why it wouldn't, or other trouble we might hit along the way? Any 'gotchas' in this scenario?