I have a hosted exchange server at XO. My office has static IP's internally. I use outlook to access the exchange server just fine. When I goto my home I have a static IP and it works fine. But if I go anywhere else, hotel, another home or anywhere using a dynamic IP it says the server can not be located.
so I'm try'n to test with an ISP called SBC. They say they block no ports, like 135. There is no firewall software or hardware.