[Mailman-Users] Newsgroup interface - prevention of spam transfer from newsgroup to emails list

[David Beaumont]

Very occasionally spam has been sent to the newsgroup which our mailman list
interfaces with.  The spam has then been uploaded to the email list and sent
out.  This can only get worse. We never get spam on our mailing list
normally because you have to be a member to email to it. Of course there is
no such restriction on the newsgroup.   Is there a simple way to restrict
postings picked up from the newsgroup to be from members of the email list
only?

Thanks