Cannot get IIS to answer OWA requests by url

Hi everyone,

I am having a tough time getting OWA to work. I have followed all the
docs on isaserver.org to implement a FE Exch server w/IIS 6.0 behind an
ISa server. At the current time, I am stuck trying to browse to
owa.domain.com/exchange. I left the dafault Exch setup with the
/exchange virtual directories under the default web site. I can get to
OWA by machine name and Ip address but I want to get there internally
by owa.domain.com/exchange. I tried using a host header on the default
web site. When I type the url I get prompted for my certificate but
then I get a 404 on the web site. This happens whether SSL is on or
not. If I want to use SSL on OWA, how do I set up IIS to answer to
owa.domain.com? I have an A record and a cname record setup for that
url as well so I think its just IIS not answering for that host header.
Please help, I am lost here.