Outlook have never supported NNTP (Network News Transfer Protocol) to
access newsgroups and probably never will. The "News" toolbar/menu
button has Outlook load Outlook Express (or Windows Mail) to do
newsgroups. To see what application gets loaded to handle newsgroups,
go to Internet Options -> Programs and see what is listed as the
Newsgroups application.
You are posting here using Windows Mail (WM). That is the Windows Vista
replacement for Outlook Express (OE). I don't use Windows Vista (thank
god) so I'm not familiar with Windows Mail. The later Windows Live Mail
(WLM) client will be the replacement for both OE and WM. Although I
have personal dislikes of WLM and won't use it until forced to, you
might consider installing that one and using it (go to
http://get.live.com and make sure you DISABLE all the other crap except
for Mail). While there were some functional changes in WLM, there were
very few additional features added to it, so WLM has the same
limitations as OE regarding its use as a newsreader client.
The Windows Vista client (Windows Mail) has its own newsgroup:
microsoft.public.windows.vista.mail
The Windows Live Mail client has its own newsgroup:
microsoft.public.windows.live.mail.desktop