DNSBLs or email blacklists are an integral part of a modern antispam system. Since their introduction in the late 90s, their have been a lot of antispam companies and organizations who have come and created their own DNSBLs. In time, tools such as RBLDNSD was built to make it even easier to make your own RBL. Since it’s very easy to consume a blocklist with a mere DNS request, they were quickly introduced into people’s existing email systems. Overtime, many of these email blocklists have become dormant, or worse, extinct. Once a perfectly working email setup with multiple DNS blocklist becomes a broken system because one of the extinct DNSBLs started returning true for the whole world, which is why it’s necessary to reviewe your choice of antispam blocklists from time to time. Over here at oikik, we use multiple DNSBLs to protect our email infrastructure, and we routinely check our email blocklists to make sure they are working well. I thought the email blocklists that are currently working well in 2019.
There are a couple more well functioning blocklists out there but the above five pretty much captures anything the others might also catch. There blocklists are maintained by well known organizations with a long history, and is unlikely to go bust overnight, breaking your antispam setup. These are IP bloclists btw, if you are looking for domain blocklists that are working well in 2019, here are our favourite picks: