Outlook Web Access redirect

I have an win2000 server with IIS setup to host Outlook web access. I want the users to use an url like webmail.company.com but the www.company.com is hosted on a SEPERATE web server that does not have OWA installed. How do I setup my dedicated web server to use webmail.company.com/exchange for outside email access? Is it a dns issue or host header.
THANKS