Hi All, I need some help here. I have 2 win2k servers setup on the same domain. Initially I had one server with both ISA Server and Exchange 2000 Server on the same machine. I was trying to get the Exchange Instant Messaging to work. I was told by Tom Shinder that this configuration was not possible and that I would need a second machine. We put together a second machine and joined it to the existing domain and we still cannot get the Exchange Instant Messaging to work. Machine A - ISA Server and Gateway Machine B - Exchange Server I have installed both the chat services and instant messaging on the exchange server. It took me a while to get the chat services to work. What I have to do was to publish the chat server on ISA Server. Unfortunately I'm getting nothing but headaches trying to get the instant messaging to work. I've created the DNS entry and I've enabled instant messaging for each user, but any user that tries to connect we are getting the same error message that the user does not have permission. When I remove ISA Server everything works fine in terms of Exchange Server Instant Messaging. As soon as I re-install ISA Server I'm faces with the same problem so I have concluded that there must be some setting that I'm missing in ISA Server. Does anyone out there have exchange instant messaging working with ISA Server? I'm pretty sure that I'll have to publish it on the ISA server like I did the chat services but I don't know if Exchange instant messaging uses any particular ports that I'll have to open. Any help will be appreciated