On a read only list I have set up

Filter= Only, *@* and
Filter= Allow, <myowndomain>

in an attempt to cut down on spam attempts.

This is fine and has cut out the approval notices but is there anyway
I can stop the resultant errors of the messages that cannot now get through,
for example:-

The enclosed message, found in the  <list> mailbox and shown under the spool
ID 5010016 in the system log, has been identified as a possible delivery error
notice for the  following reason: mail origin is listed  in the "Filter=" list
header keyword (or its default value for the <list> list).

Return-Path: <[log in to unmask]>

Any help would be appreciated.

Wayne