<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; ">Heres what I want to do<DIV><BR class="khtml-block-placeholder"></DIV><DIV>I have a new mail spam filter machine I want to test before I change the mx records</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>this machine I will call A receives mail and forwards it to B</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>currently B is the MX</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>So what I'd like to do is using iptables :</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>route port 25 traffic currently going to B --> A except when it comes from A</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>I tried</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><FONT class="Apple-style-span" face="Lucida Grande" size="3"><SPAN class="Apple-style-span" style="font-size: 11px;">iptables -t nat -A PREROUTING -p tcp -m tcp -s ! A --dport 25 -j DNAT --to-destination A</SPAN></FONT></DIV><DIV><FONT class="Apple-style-span" face="Lucida Grande" size="3"><SPAN class="Apple-style-span" style="font-size: 11px;"><BR class="khtml-block-placeholder"></SPAN></FONT></DIV><DIV><FONT class="Apple-style-span" face="Lucida Grande" size="3"><SPAN class="Apple-style-span" style="font-size: 11px;">but this didn't work</SPAN></FONT></DIV><DIV><FONT class="Apple-style-span" face="Lucida Grande" size="3"><SPAN class="Apple-style-span" style="font-size: 11px;"><BR class="khtml-block-placeholder"></SPAN></FONT></DIV><DIV><FONT class="Apple-style-span" face="Lucida Grande" size="3"><SPAN class="Apple-style-span" style="font-size: 11px;">suggestions ? </SPAN></FONT></DIV><DIV><FONT class="Apple-style-span" face="Lucida Grande" size="3"><SPAN class="Apple-style-span" style="font-size: 11px;"><BR class="khtml-block-placeholder"></SPAN></FONT></DIV><DIV><FONT class="Apple-style-span" face="Lucida Grande" size="3"><SPAN class="Apple-style-span" style="font-size: 11px;">Dave</SPAN></FONT></DIV></BODY></HTML>