The effectiveness of black-listing mail servers is questionable. The overall spam volume does not appear to be impacted and keeps going up. The argument that the amount of spam would rise faster without blacklisting is nonsense. Blacklisting affects a very small percentage of emails that are in a gray zone between spam and ham, such as emails that I send to a personal mailing list with 50 members.
The large professional spammers probably only laugh about blacklisting efforts. With botnets distributed worldwide to millions of computers, there is no longer a need to rely on individual senders.
So why do big players like GoDaddy still engage in email blacklisting? One side effect of large providers blocking the IP addresses of small providers is that they are hurting the small providers’ business. Customers are unhappy, and since there is no solution for the small provider to permanently get their mail servers unblocked by the large providers, customers will eventually move their account to the large provider.
Blacklisting of email servers hurts the competition in the provider market. It is a tool that drives small providers out of the market, and will lead to a consolidation that is not good for consumers.