An entity called McFadden Associates had been publishing two different, spamtrap-driven DNSBL zones starting from October 2003. Almost ten years later, it appears that these blocklist zones are no more.
The McFadden CSMA blocking list encompassed two different DNSBL zones.
The primary zone, bl.csma.biz, contained only "aggressive" hosts that
have spammed repeatedly during a short (recent) timeframe. An additional
zone, sbl.csma.biz, had a broader listing criteria, noted by
the publisher as more suitable for scoring in a filtering system than
As of January 2013, querying either zone will result in a false positive
response, showing that an IP address is blocked, due to a wildcard DNS
entry. This means that you should immediately stop using either DNSBL in
your spam blocking configuration, otherwise you will reject all inbound
mail, legitimate or not.
It's fairly common for a list, when dying, to intentionally or
un-intentionally "list the world," answering any DNS lookup request with
what amounts to a "yep, that's blocked" response. This regularly causes
problems for unsuspecting email system administrators who may still be
querying blocking lists that are now out of commission. That's why it's
important to periodically review your inbound mail server's
configuration to revisit what DNSBL lists you might be using and whether
or not it makes sense to continue to use them.
case, these lists are no more, and should be removed from any mail
server configurations where they may still linger.
reached out to the one-time publisher of these lists, and I will
follow up with more information if he's able to provide more details.