Get in touch with Gary VanderMolen, Microsoft MVP (Mail). He had the same issue
(everything worked except postings did not show up ) and he was off from posting for
a few days because of it.He solved the problem and maybe it is the same as with you.
Below is a snip from his return post of today.
He posts here in this group and also in windows.vista.mail
Please Reply to Newsgroup for the benefit of others
Requests for assistance by email can not and will not be acknowledged.
"Lanwench [MVP - Exchange]" <LanwenchMVPExchange@newsgroup> wrote in
Much of what I've posted since January 21st has gone into a black hole.
After running many tests it turns out that only the newsgroups on the NNTP
server msnews.microsoft.com ("Microsoft Communities") are affected.
Posting to newsgroups other than the public Microsoft ones was normal.
After much troubleshooting, the logical conclusion was that my Microsoft
Communities account in Windows Mail was corrupted. Yet all the sent
posts saved to Sent Items, without any error message. Deleting the account
and recreating it did not fix
the problem. Tried two other newsreaders,
Agent and Windows Live Mail, same result. Tried both Vista and Windows 7
computers, same result. Posting to the test newsgroups resulted in about a
50% success rate, with no rhyme or reason.
Nothing has changed on my end, but am trying again to see what happens.
Gary VanderMolen, Microsoft MVP (Mail)