Hi, I will have my new external namespace webmail.domain.com NAT'd in the firewall to my casarray and have my new legacy.domain.com exteranl namespace NAT'd to my exchange 2007 CAS server. I still have my exchange 2007 external namespace NAT'd to my exchange 2007 CAS server. Our firewall won't allow us to NAT 2 external IP's to the same internal IP. How can I get around this?

Thank you. So this is what I should do: Current: exchange2007.domain.com (OWA, Activesync for current exchange 2007 environment). Points to current exchange 2007 CAS via Firewall NAT. current name of exchange 2007 CAS server. New: webmail.domain.com (OWA, Activesync for new exchange 2010 environment). Will point to new exchange 2010 CAS (internal casarray) via firewall NAT. legacy.domain.com (OWA, Activesync for old exchange 2007 environment). Will point to old exchange 2007 CAS via Firewall NAT. exchange2007.domain.com (OWA, Activesync for current exchange 2007 environment). Currently points to current exchange 2007 CAS via Firewall NAT. Remove and do not use anymore. Current name of exchange 2007 CAS server. Is this correct, just completely get rid of the current exchange2007.domain.com namespace and firewall rule and replace it with legacy.domain.com? So everything that currently points to exchange2007.domain.com will automatically go to my old exchange 2007 CAS server through the legacy.domain.com namespace? If I remove the exchange2007.domain.com namespace form external DNS and remove its firewall NAT how will anything pointing to exchange2007.domain.com resolve? I apologize for my ignorance with understanding this concept. I really just want to leave exchange2007.domain.com and not create a new one called legacy.domain.com because I just don't understand how externally "legacy" can be resolved if I remove "exchange2007". All of our activesync devices are setup with "exchange2007.domain.com" not "legacy.domain.com". If I could just NAT both "legacy" and "exchange2007" to the same internal IP (my current exchange 2007 CAS server) I would feel the safest, but my firewall guy says our firewall won't allow for the NAT'ing of 2 external IP's to the same internal IP.