connection to servers

Hello everybody,

I just installed TB portable on a USB memory device, so I can use it on different computers I work on. I got it going on one computer that is connected directly to the internet (without proxy), and it works flawlessly there.

then I took the USB stick to another laptop, that is running Vista behind a corporate firewall. No luck there. I get error messages from each of the mail servers I am trying to connect to. I can use Firefox on the same computer by specifying a proxy server. I have tried to specify the same proxy server for TB, but still can't get through. Is there anything I can do to use the device/application on that network? Do I have to perhaps specify a different port for TB to connect to the servers (gmail, hotmail, and a couple of others)?