To simply divert messages to the request-address that don't come from current subscribers you can use the same mechanism smartlist uses to restrict postings, i.e. formail/multigram and the dist file (define $SPAMTRAP to be a file of your choice) :0: * !? formail -X"From " -xFrom: -xReply-To: -xSender: -xResent-From: \ -xResent-Reply-To: -xResent-Sender: -xReturn-Path: | \ multigram -b1 -m -l$submit_threshold -L$domain \ -x$listaddr -x$listreq dist $SPAMTRAP if you want to be a little less restrictive you can use (as was mentioned by Jim Osborn) an approach which uses SpamAssassin (SA) to check for the spamishness of messages that aren't from subscribers: WHITEU=dist FROM = `formail -IReply- -rtzxTo:` :0 * ! ? fgrep -i $FROM $WHITEU { INCLUDERC=spamcheck.rc } -- where spamcheck.rc is tuned to whatever spam-finding package you prefer, for instance a simple-minded (and low-volume) SA approach could be: :0fw | /usr/local/bin/spamassassin :0: * ^X-Spam-Status: Yes $SPAMTRAP Rich