As reported on the mailop mailing list on Friday May 25, 2018, the blacklist at dnsbl.cyberlogic.net now contains a "wildcard" DNS entry, effectively blacklisting the entire internet. If you use this DNSBL in your mail server configuration, you should remove it immediately, as it will impede your ability to receive legitimate mail.
Cyberlogic's DNSBL web site is off line today, but the Internet Archive suggests that they had a DNSBL information website that was first observed in 2008. That website provided this information regarding listing criteria: Our DNSBL protects the Cyberlogic Network from incoming email from undesired sources (ie mail relay). These sources have often sent SPAM or VIRUS emails to Cyberlogic customers and resulted in a complaint. This list also defines sources in abuse of Cyberlogic Terms of Service & Network Policies."
It is not clear to me if this DNSBL was meant to be for public use. I found one reference that suggests it was not. I suspect it may have been publicly available in the past, and it shows up in various listing / checking tools, and I think mail admins may be tempted to include it in their mail server configuration. So I think it makes sense to note it here to warn people that using this DNSBL as a spam filter in their mail server will result in rejecting legitimate mail.
If you have more information about this blacklist or its status, please don't hesitate to contact me and I will update this post as appropriate.