Thanks for your replies. Cacosapo, those two rules at the end of your post would work for all services then? So for example, if I also wanted to put a webserver online, I would open port 80 incoming and outgoing (like the two first rules in your post), and the other already existing rules would take care of the local ports? Please correct me if I misunderstood.

kr5kernel, how can you tunnel a connection through port 25 to a different service? I didn't know that was possible..