If you are migrating Public Folders from an Exchange server you should first make sure that the existing folders have been converted to real news groups
running suck orignewsserver -bp -hl localhost -A -c -y post_filter.pl
where orignewsserver is your original newsserver (could be your exchange server) postfilter.pl is a script that is being used because Exchange does not give any Path: values, Inn complains for not having thes values and refuses to post the messages .