I'm having a bit of a problem with an iMac as follows: It has full internet connectivity and there's no problems anywhere apart from when I try to connect to a particular exchange email server using the servers url or public IP. The server is on the same network as the iMac and if I try to connect to the OWA by entering the private IP, 192.168.x.x, then it connects fine. If I try to connect to the URL, https://mycompany.co.uk/owa, then nothing, it just times out. It is getting the correct DNS reply for the public IP, 188.x.x.x, and if I substitute this in the address bar then still nothing. All the other computers on the network (Mac + Linux + Win + iPhone) work fine with email clients and with the web access OWA. Also access from the internet (other office/home etc) works fine too. It's just this one iMac and I have no ideas why only the public address will not connect? Finally when I try all this having unplugged the ethernet cable and run it with Wifi then it works. I also doesn't matter what IP address the ethernet port is on, doesn't work on any. Any ideas?