The maintainers of the "NixSPAM" blocklist (with a DNSBL zone of ix.dnsbl.manitu.net) have decided to shut down. As of January 16, 2025, their website at nixspam.net states that, "With a heavy heart, we have decided to discontinue the project ix.dnsbl.manitu.net." This matches a statement posted by the blocklist's maintainer on X.
No further information is available at this time. The website indicates that further information may be coming. In the mean time, I suggest that you remove this DNSBL from any spam filtering or IP reputation checks as soon as possible, as when blocklists shut down, they often can end up with "wildcard DNS" that can cause unexpected and unwanted inbound email delivery impediments.
Jan-Piet Mens previously described the NixSPAM thusly: "The NixSPAM black-list is a DNS block-list created by Bert Ungerer of ix. It contains automatically generated entries from open proxies, relays, dialup gateways, etc., and [...] Black-listed entries are automatically removed after 12 hours if no further spam from that particular source is detected within that time frame."
The NiXSPAM blocklist appears to have launched in 2003. Congrats to iX for a nearly 22 year long run.