Blocklist check
A blocklist cannot tell you it has stopped working. A zone that was shut down answers nothing, which is the same answer it gives for an address that is not listed, so every checker still querying it reports the whole internet as clean. One that refuses your resolver answers something to everything, which reports the whole internet as listed.
Your address is never sent here. The lookups go from your browser to a public DNS-over-HTTPS resolver.
Why a list gets refused before its answer is read
RFC 5782 requires every conformant list to contain 127.0.0.2 and to not contain 127.0.0.1. Those two queries separate a list that is working from one that is not, and they are the only way to tell the difference from outside.
- Answers neither. The zone is dead or refusing. SORBS was decommissioned in 2024 and its zone stopped answering, so every tool still asking it has been reporting a clean result ever since.
- Answers both. The list is returning something other than list data. Spamhaus answers 127.255.255.254 to any query arriving through a public resolver, and a checker counting any answer as a hit reports every address as listed.
- Answers the wrong one. The return codes do not mean what a blocklist query means. Some reputation services publish on the same interface without following the same convention.
In all three cases this reports that it could not determine an answer, and says which. A blocklist result you cannot trust is worse than no result, because you act on it.