> I have found that greylisting based on the Spamhaus sbl-xbl list > massively reduces spam. Setting that up on my backup MX > resulted in all traffic through it stopping when my primary MX is > up. James, Are you using greylisting or blacklisting with Spamhaus? My understanding of blacklisting is that blacklisting uses a DNS blacklist, such as Spamhaus. My understanding of greylisting is when your MTA sends back a temporary failure the first time in X number of days where it sees a new sender/receiver/mail server IP address triplicate. Please clarify. Thanks, Barry