Trying not to ramble here

I have an E-smith (ver6) server at work acting as a gateway, vpn server and aother "stuff".
On the same network I have an exchange server (I know, but the boss liked it and it will look nice on my CV). The E-smith box is not the PDC, so after setting appropriate IP addresses on clients connecting via VPN I am able to connect to PCs within my network just fine using IP or network neighberhood. I can also use the hostname of my exchange server to connect to it using Outlook.
Troublke is, my directors want Outlook web access. trying to set this up has been problematic, as using the IP address seems to upset outlook, and using the hostname seems to get caught by squid on the e-smith box which tells me that the hostname is invalid.
Any idea how I can persuade squid or e-smith to pass the hostname onto my exchange server?
TIA
Rob