John Levine wrote:
A DNSBL that blocks a single IP at a time, like the CBL and XBL, would be unworkable. A typical v6 setup allocates a /64 to each host which allows various sorts of clever self-configuration, but also means the host can easily use a different IP address for every connection it ever makes. (At one address per millisecond, it would take 500 million years to run through a /64.)
Very well stated! I think we may say that, for any practical concern, tracking IP addresses won't have clear advantages over tracking registered domain names.
Rick's very detailed list provides many good hints. However, sooner or later somebody should state some clear instructions for running an MTA. I mean something that a company, an association, or even a household can easily set up and maintain, rather than an art/craft requiring arcane esoteric skills. In particular, tracking registered domain names allows to keep non-DNS settings unchanged through a change of connection provider(s), which seems to me a worthwhile simplification.