Previous updates follow.
This post in the newsgroup news.admin.net-abuse.email, and my own testing both confirm that any DNSBLs running under completewhois.com are dead, no longer available.
If you were utilizing any DNSBL under completewhois.com, I recommend that you immediately remove it from your configuration. Time outs waiting for DNS replies will slow your inbound mail delivery. I have also heard mention of a wildcard DNS entry, which would result in any user of this now-dead list rejecting all of their inbound mail. I was not able to personally confirm the wildcard entry at the time of this posting.
This includes the zones invalidipwhois.dnsiplists.completewhois.com, hijacked.dnsiplists.completewhois.com, bogons.dnsiplists.completewhois.com, and combined-HIB.dnsiplists.completewhois.com.
Some SpamAssassin rules check completewhois.com DNSBLs. These queries are timing out, and are likely to be causing slower than expected mail delivery. The rules in question are: RCVD_IN_WHOIS_INVALID, RCVD_IN_WHOIS_BOGONS, RCVD_IN_WHOIS_HIJACKED, and RCVD_IN_WHOIS. At this time I would recommend disabling these rules.
Not all error messages explicitly refer to the full zone name. It's safe to assume that anything checking for "Bogons" is actually checking a completewhois.com DNSBL, and therefore would be returning a false positive response, or causing mail delays due to lookup timeouts. As an example, bounces with the error message "5.7.1
What happened to the list? Why did it go away? I'm not sure; this list is not run by a group that I have any contact with, and additional information is currently difficult to come by.
I'll be sure to update this page with more information as it becomes available.