Yes of course, it's mandatory for the new fibre protocol used with the 10gb connections. I went from the original fibre router Internet-box (1) to the new Internet-Box 3. It uses a different fibre module.
Thanks a lot for the suggestion. I just tried again, and it seems that everything is back working again. I suspect that Swisscom had a routing issue somewhere.
For your info, my newsgroup client connects on several ports, with 2 remote connections using SSL to port 443. If I was to port forward all 443 traffic to a specific host on my internal network, then it would break web browsing for all other network clients! uPNP should be perfectly capable of working out which traffic goes to which port on which host, based on network packets.