I hate spam

I have tried a number of solutions to the problem of keeping spam off of my systems over the years. I've had my e-mail address for quite a few years which means it has been harvested a number of times. Because of this, I get quite a bit of spam. Until I instituted my latest set of changes, I was getting between 200 and 300 spam e-mails a day.

I have no intention of giving up or changing my e-mail address so keeping spam off of my system has become something of a personal battle for me. One thing nice about running my own mail server is I can use any weapons I can find in that fight.

Up until recently, I have relied on just running DSPAM on my mail server. It is fairly effective and, together with the spam filter built into Thunderbird (our e-mail client), we still only had one or two spams a day reaching our inbox. The downside was that wading through all of the spams in DSPAM's quarantine was becoming a real chore which became overwhelming if we were unable to clear it for a few days due to travel. It also meant that all of that garbage was taking up space on my server.

Before running DSPAM, I had relied on a combination of Real-time Black Lists (RBLs) such as SpamCop and the Open Relay Database (ORDB). When the spammers moved to using botnets, these became less effective since they relied on the source of the spam being known. This lack of effectiveness drove me to try DSPAM.

The CentOS mailing list recently had spam prevention come up as a thread for discussion. The person starting the thread was primarily objecting to the space the spam was taking up and wanted a solution that would not even let it get delivered. A couple of people responded with a recommendation of several RBLs including SpamCop and ORDB as well as spamhaus. I remembered that ORDB had shut down some time ago so I was a little skeptical but I decided to try the suggested RBLs.

My memory was correct about ORDB but the combination of SpamCop and SpamHaus has reduced the amount of spam the actually reaches DSPAM to about a quarter of the previous level, The following graph was generated by DSPAM showing the reduction:

I cut in the changes to my sendmail configuration at a little before 08:00 am on the morning of March 5th so the spam count for the 5th still includes the spam I had received prior to making my change.

The additions to my sendmail.cf file are as follows:

dnl RBLs to stop spam before it gets here:

FEATURE(`dnsbl', `bl.spamcop.net',
`"Spam blocked see: http://spamcop.net/bl.shtml?"$&{client_addr}')dnl

FEATURE(`dnsbl', `sbl-xbl.spamhaus.org',
`"571 ACCESS DENIED to <"$&f"> thru "$&{client_name}" by /spamhaus/ ;
Please see http://www.spamhaus.org/sbl/'")dnl

If you decide to use this suggestion for a commercial operation, please donate to both SpamCop and Spamhaus. Even if you're not a commercial operation, please consider donating.

Cheers,
Dave