Based on the post on http://ipv6-or-no-ipv6.blogspot.com/200 ... ntage.html , (a lot of) Vista users appear to have "under water" working IPv6 connectivity. Easy test: visit the URLs mentionned in the blog post. Remark: as mentionned in the blog post, you need to use litteral IPv6 address in your webbrowser and in ping.
If that works, just fill out news.ipv6.eweka.nl in SABnzbd, and start downloading. Retention is about 170 days.
I justed tested it, and had a succesful download with "[Avg-Speed]: 259kB/s". Not bad for an easy and free download service. :-)
Please give feedback. If it works, this info can be added / injected into the thread "Free Newsservers" (http://forums.sabnzbd.org/index.php?topic=51.0)
(Technical remark: SAB does not need the litteral IPv6 address and is OK with the FQDN. Apparantly SAB (or python?) does it's own resolving, and does not rely on Vista's resolving settings?)

