Dear All, I'm just a newbie in this list and try to seek answer and help to my problem. I have requirement from my user to access exchange (OWA) in internal Network via ISA server from internet, I recently use ISA server for proxying outgoing web access and I also want to be able to cache incoming request (reverse caching). I have the following items : 1. 1 Firewall heading the Internet which having 3 NIC (external, DMZ, internal) 2. 1 ISA server installed on cache mode have 1 NIC, which sitting in internal network (Internal_IP_Of_ISA) and has its IP NATed by firewall to have public IP (External_IP_Of_ISA) 3. 1 Exchange server sitting on internal network (same IP segment with ISA server), its default gateway is following the same gateway with any server in same segment I configure my ISA server as follow : - My ISA server is joining my Windows Domain - I set Incoming Web Request to authenticate every user when connected, using Integrated mode - I follow Shinder Section to publish OWA as follow : * Create destination set called OWA, consist of (Internal_IP_Of_ISA/exchange/*, Internal_IP_Of_ISA/exchweb/*, Internal_IP_Of_ISA/public/*), my opinion to use internal IP is the connection that reached the ISA server already translated by firewall to search the translation of External_IP_Of_ISA, am I right ???? * Create a publishing rule called AccessOWA, as follow : Destination : Selected destination set, I select OWA Action : redirect to Exchange server IP Bridging : (left as default) Applies To : any request Then I try to access it using I.E 501 or 5.5 to http://External_IP_Of_ISA/exchange/ , I got following error : HTTP 407 Proxy Authentication Required - The ISA Server requires authorization to fulfill the request. Access to the Web Proxy service is denied. (12209) Internet Security and Acceleration Server Technical Information (for support personnel) Background: The gateway could not retrieve the requested page. ISA Server: MYLOVELYISA Via: URL: /exchange/ I suspected it caused by translation of Public/Private IP , then I try to access it from internal network using http://Internal_IP_Of_ISA/exchange/ , which is exactly match with what I put on destination set, but the result is same as before. Please Gurus shed a light on me to solve this problem, any advice will greatly appreciated Best regards, Edo