Blacklists operate using DNS system where a blacklist publishes a set of IP addresses that are blacklisted. We query these lists in real-time to give you a consolidated report of the blacklist reputation of and IP address. Sometimes a DNS server at a blacklist operator may get out of sync with the entire pool or the pool may get out of sync with the database. Regardless of the root cause, we always display what we receive when we query the blacklist providers’ DNS servers.

Currently, we are noticing On Friday, we noticed some issues where the Blacklist NoSolicitado is showing some IP addresses blacklisted and then quickly delisting them. These bounces are affecting customers with blacklist monitors and those searching IP addresses. We will update when there is more information.

Update:  NoSolicitado has updated their DNS and we are no longer showing false positives of listing/delisting bounces.  If you are on NoSolicitado, it is a legitimate listing.