For historical reasons, the SURBL public nameservers were serving
individual lists ab, sc, ob and ws in addition to multi. However
these individual lists have all been deprecated in favor of multi for
several years since multi contains all lists. Traffic for the
individual lists is relatively very low, and no one should be using
them any more, so in order to reduce unnecessary and redundant network
traffic we will be turning off public nameservice for the individual
lists on February 28th, 2009.
Everyone should be using multi.surbl.org instead, and this has been
the case for many years now. Therefore if anyone is using the
individual lists, please stop doing so and use multi instead. A
single query to multi will check all SURBL lists.
http://www.surbl.org/lists.html
Cheers,
Jeff C.