The homepage and also other pages on the site https://pixhawk.org/ contain links to the google mailing list that seems to be depreciated. The links are in the side bar and at the bottom of the homepage in section Contact & Credits.
Thanks for pointing it out.
@hamishwillee (or @LorenzMeier) could we get the links on pixhawk.org updated?
Thanks for that. I have fixed those links to point to http://discuss.px4.io. @dagar should I have changed to point explicitly to the firmware section?