Moving to Real time Black hole Lists (RBL) to cut down spam By Peter M. Abraham July 2003 SPAM (unsolicited email) continues to escalate with researchers indicating the cost to consumers at over $10,000,000,000 ($10 billion) U.S. dollars in 2003 alone. Several months back we instituted SPAM tagging where we would tag mail suspected as SPAM so that you could filter these messages into a quarantine area for later review, and potential deleting. Shortly thereafter, we implemented an internal SPAM guarding system that would block agencies sending large volumes over short periods of time through our servers.  The SPAM companies shifted to changing their email address for each email sent so that no single email address would be used for more than five emails within a five minute time SPAM. We then started blocking absolutely confirmed SPAM companies at our firewall.  The list of blocked IP addresses grew to almost 1,000 in less than four weeks with 100 to 200 new addresses being added per week. There was always the danger of accidentally adding a dial up provider's IP address to the firewall, and thereby blocking legitimate email when the real SPAM company moved to another IP from the same or different provider. In the mean time, we were receiving complaints from our customers that some are getting between 100 to 500 SPAM messages a day.  Yes, they are tagged; but it is still taking up their bandwidth and disk space. Yes, SPAM does cost you in bandwidth and disk space.  The SPAM messages that wait on the server for pickup, takes up disk space you could be using for your own files. When you download SPAM messages, your bandwidth is going up; and, this may cause you to go over your monthly bandwidth allotment (which will cost you real dollars). On July 11, 2003 we started using Real time Black hole Lists (RBL) in order to block SPAM prior to it getting into your in box. Since then we've been blocking approximately 30,000 to 50,000 email messages per day per email server (we have four email servers).  That adds up to blocking 120,000 to 200,000 SPAM messages per day. Chances are high by now, you are probably thinking about two very important questions: Why am I still getting some SPAM?   Is it possible that valid emails are being blocked? You may still be getting some SPAM become the SPAM individual or agency is not yet listed in the RBL (Real time Black hole List). Zero email is lost because of the use of RBL.  If a sender's mail server is listed within an RBL, they will receive an error message stating why they cannot send an email to you. What the sender is told will depend on which real time black hole list (RBL) their mail server is on: Those in Spamhaus.org may receive something like http://www.spamhaus.org/SBL/sbl.lasso?query=SBL9700 Those in SpamCop.net may receive something like http://spamcop.net/bl.shtml?203.192.10.7 Those in dnsbl.njabl.org and opm.blitzed.org, will receive either "open proxy" or "relay proxy" as the error message. Those in rfc-ignorant.org would receive an error message as to how their mail server is not compliant with RFC standards. If you believe a customer, partner, vendor, family member, friend, or otherwise legitimate person or company is receiving an error message, please let us know the following information: Complete email address of the sender. The name of the sender's ISP or mail service provider. The exact error message (if possible). This information will allow us to verify whether or not our systems are causing a block, to immediately remove any bad blocks, or to work with the RBL providers to get the mail server provider unlisted from the RBL. Please contact our support department if you have any questions.