I'm setting up Exchange 2007 using Forefront TMG for client traffic including autodiscovery. All of our IE clients are set to use a linux based proxy. Using the Test E-mail autoconfiguration tool in Outlook fails if IE is set to the proxy, but works perfectly if the proxy is left blank. I've put exceptions into IE when the proxy is set and it still fails. I'm testing a rule in TMG to allow anything from the proxy, but it doesn't seem to help. Does anyone know how to deal with this?