[Mailman-Users] Please help - newsgroup gateway woes

[Mike Avery]

I'm sorry to ask this again, but I am at wits end.  And I'm getting beat 
up by my users and spamcop....

For some time I've been using Mailman to gateway a few Usenet 
newsgroups to mailing lists.

Recently, my server and Mailman were used to spam several of those 
newsgroups.  Spamcop was upset and shared the upset with me and 
my ISP.  Until I can secure the Mailman gateway, I have shut down the 
gateway, which has my users upset.  They, like me, don't like most 
news reader software.

Right now, I'm running Mailman 2.1.1 under FreeBSD 4.7 using Postfix 
as my MTA.

Here's where I am now.  If I don't do anything about security, 
anyonecan post to the mailing list and their posts also go to the 
newsgroup.  Which opens the newsgroup to spammers, and me to 
abuse from Spamcop and other people who are trying to minimize 
spam.

If I restrict posting to the mailing list to only members, then all 
messages from the newsgroup are treated as messages from people 
who aren't subscribers.  Which means that they could be automatically 
discarded or held for my approval.  Neither option works for me.  I don't 
have time to personally approve all the posts from the newsgroups.  
And even if I did, I could mess up and accidentally approve a post from 
a spammer that came through the mailing list.  I prefer to automate 
things.

So, is there a setting I'm missing that will allow me to let only members 
of the mailing list post to the mailing list, and let all messages from the 
newsgroup be treated as if they were from members of the mailing list?

Thanks,
Mike