I wouldn't condone usage of SORBS' lists, because they sometimes use robots to automatically list things that have little rational basis for being listed, which causes problems. But it may be hard to convince your mail recipients to avoid the same. Commonly, providers may give un-assigned subnets generic PTR records like "isp192-168-0-1.somedomain.com" over their IP space. SORBS automatically lists these in the DUHL. And does not automatically remove them later, when the reverse zone is populated with final hostnames. Legitimate mailservers that do not originate spam routinely appear in the DUHL (and get blocked by users of the list).
How would you like it if a non-customer came to you demanding resolution to a problem with a free service you provide? Would you drop everything, and give that non-customer the same service you give a paying customer?
That depends on the service. The DNS root servers provide a free service to internet users who aren't customers. If those servers all started directing users' .COM, lookups to an incorrect TLD server, so nothing resolved, people would be upset if $root_server_operator told them to wait 2 weeks. People who consume a blacklist might get that service for free, but they only do it on reliance that the blacklist follows the policies that the maintainer had published for their blacklist. In other words, that they provide what they say they are providing, and not something different. The expectation of timeliness arises, because internet applications, services like the web and e-mail are time-critical, no ability to send e-mail may mean lost revenue. An improper blacklist entry (or even a proper one) does direct, immediate, and serious damage to the party listed, and this injury is caused directly by the actions of the blacklist provider maintaining the list entry. I would suggest blacklist services have a moral duty to take reasonable measures to ensure they are not inflicting excessive, easily avoidable damage on innocent third parties, with stale or erroneous entries in their lists. If people believed a blacklist did not take reasonable measures to correct errors quickly, then it would be understandable that their reputation suffers. -- -J