Hi! 10.10.4.1 is Front-End Exchange (also RPC Proxy) 10.10.4.254 is the internal IP address of ISA Server. Client tries to access to Front-End EXchange by using RPC over HTTPS Who can comment these 4 lines in the ISA Server 2004 log file? ISA, 10/18/2004, 14:15:15, TCP, 10.10.4.254:1846, 10.10.4.1:443, 10.10.4.254, Local Host, Internal, Establish, 0x0, -, HTTPS, N, 0, 0, 0, 0, -, -, -, -, -, -, -, -, 296, 1141, -, -, - ISA, 10/18/2004, 14:15:15, TCP, 10.10.4.254:1847, 10.10.4.1:443, 10.10.4.254, Local Host, Internal, Establish, 0x0, -, HTTPS, N, 0, 0, 0, 0, -, -, -, -, -, -, -, -, 296, 1142, -, -, - ISA, 10/18/2004, 14:15:15, TCP, 10.10.4.254:1846, 10.10.4.1:443, 10.10.4.254, Local Host, Internal, Terminate, 0x80074e20, -, HTTPS, N, 847, 847, 420, 420, -, -, -, -, -, -, -, -, 296, 1141, -, -, - ISA, 10/18/2004, 14:15:15, TCP, 10.10.4.254:1847, 10.10.4.1:443, 10.10.4.254, Local Host, Internal, Terminate, 0x80074e20, -, HTTPS, N, 812, 812, 420, 420, -, -, -, -, -, -, -, -, 296, 1142, -, -, - Client cannot access Exchange by using RPC over HTTPS. Best Regards Mustafa