I want to install Ex2010 and co-exist with Ex2003. If I do this will it after the install immediately re-route the messages to CAS and change the the existing internet facing web page to legacy.domain.com?? I read somewhere when you install EX2010 it becomes part of the Ex environment. IF I don't have a SAN SSL yet will also give a security error to the Outlook 2010 since they will now goto autodiscover.domain.com? So the basic question is when you install EX2010 do you have time to play around with the internet, SSL any firewall issues etc. or do you have to get EX2010 integrated ASAP!