Our organization is currently using an Exchange 2007 server. We have set up an Exchange 2010 environment in the same forest and would like to start testing it before we migrate our mailboxes over. The question I have is with regards to DNS. If I add the Exchange 2010 MX record with a lower priority, I'm worried that mail servers may query this server even when the primary is up. Am I right that this may happen? If this is the case, what is the best way to set this up? I don't want to set it up on a sub-domain as I don't want to have to change all of the certificates when we go to migrate. I also don't want to route all 2010 emails through the 2007 send connector as this doesn't fully test the environment.