> However, a new threat comes from spammers who spoof the list
> address itself. The LISTSERV (v 1.8d) dutifully sends back a
> message to (who it assumes is the) unsubscribed poster with
> the often obscene posting included below the error message.
>
> This means, of course, that the message still gets through. I tried a
> number of ways of changing the list config. that did not seem to help
> and finally resorted to a rather inelegant method which is to quietly
> subscribe the list's address to the list, quietly set it to nomail and
> then quietly to review.

In the list header:

Filter= Also,listaddress@*, listserv@*