Are there less anti-spam DNS blocklists than there used to be?
Once upon a time, back when I paid a fair amount of attention to anti-spam stuff, there were quite a lot of DNS blocklists. Some had good reputations and some were more colourful, some were conservative and slow-moving while others were much more aggressive and fast to block, but there were any number of them that many people looked at. I did enough in this area that I wrote a script to look up IP(s) in all of the worthwhile DNSBLs that I knew about.
Over the past few years I've been steadily removing DNSBL after DNSBL from this script (and sometimes from the mailer configuration on my office workstation), most recently NJABL. And it doesn't seem like new DNSBLs are replacing them in a transfer of the guard from the tired to the new and eager; instead the collection of worthwhile DNSBLs just seems to have been diminishing.
(I confirmed this with someone I know who is more in touch with email anti-spam than I am these days; his view was that it was basically down to Spamhaus (and its data sources). I'm still slightly broader than that, as I sometimes look at SURBL for spam website names.)
Now I'll admit that this may be somewhat illusory in that I'm not looking in the right place for modern DNSBL discussions; after all, one of the reasons I stopped paying attention to the field is that my usual information sources turned into sewers. I have some indications that other sites out there use additional DNSBLs (although none that I really consider worthwhile ones and none that are all that new).
I have some theories on what this diminishment of DNSBLs may mean but I'll save them for another entry (partly because I want to think about them some more).