I'd almost be willing to bet that the posts are being filtered because of
your "no-ip" address. I had a similar problem with mail being bounced
(especially by AOL) which seems to have been completely resolved by
getting a "real" domain name. When I first switched to broadband (canopy
satellite) the tech told me that their dynamic IP addresses are
practically permanent so I shouldn't have any trouble running servers...
Whether that's valid for all broadband ISPs or whether it would help in
your case, I have no idea, but it might be worth looking into.
-s