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SpamAssassin 3.0 and higher use multi.surbl.org instead of individual lists such as sc.surbl.org. This is preferred since a single query to multi will get results for all of the individual lists. As of March 1, 2009, public DNS service for the individual lists is disabled, and only multi.surbl.org is served. Therefore please use multi, as is the default for SpamAssassin 3.0 and newer versions. Said another way, if you are using SpamAssassin 3.0 or newer with the default SURBL rules, then no changes are needed. However anyone using SpamAssassin 2.6 should upgrade to 3.X.