I will be migrating to Exchange 2010 in a few days. I want to have Exchange installed and ready to go before then. I know coexistence during migration is not a problem, but I also know that 2010 is supposed to be the front-end and it passes mail to 2003. Can I install 2010 and leave mail flow as-is to 2003 until I am ready to make the switch? I want my DNS records, etc to remain going to 2003 until I am ready. I am assuming this is ok, but I need a confirmation. Thanks.