At Raymond's suggestion, we are now making available gzipped versions of the rbldnsd zone files. They are significantly smaller than the original text versions. This is to correspond to the recent addition of gzipped file support to rbldnsd:
http://www.corpit.ru/mjt/rbldnsd/NEWS
Note that most installations and applications should only need to use the multi.surbl.org list, since multi includes all production lists.
Jeff C.