Not much to add here except that most email systems like Orange only allow sending when you are on their network.
Remember this is a widely discussed issue. Orange must tell you how to do this, they may actually not allow it!
Whenever I am logged into another Wifi (eg on holidays etc) away from home, I get the same problem: I continue receiving emails, but cannot SEND. My provider is Orange and PC is on Windows 7 (with Livemail). I have 2 email addresses but whether I use my Orange or Gmail one, the problem remains. This message may get onto the forums or may not, let's see, but I may not be able to answer you until I get home in a week's time, unless I can do something now to heal this problem.