[Alvaro]

You are probably right, but I don't count on it. This environment is quite rigid, unfortunately.
Another way forward would be to be able to configure manual proxy settings, so I can ssh-tunnel the connection (this can be done e.g. in the dropbox client).
My current workaround is to define a network location in my mac using the ssh tunnel as proxy. But this makes my other corporate connections fail, so this means I have to manually sync OF from time to time by changing the network location (and launching the tunnel from the terminal). It's a bit annoying, but it works.