Earlier quoted context omitted.
As a practitioner, I can tell you that this proposal would be quite a bit behind state of the art for email spam filter accuracy. For example, there's a surprising amount of legitimate mail that gets sent without authentication, and which you don't want to block because your end users will get mad if it goes missing. I may also point out that "reputation scoring for netblocks" is the exact problem the original blog p…
if netblock reputation were known small non-spam senders would congregate, this would help weed out the spammers. but google et al. don't provide any feedback. nor any way to build reputation for your IP. (where are all the staking blockfoo chainbar solutions? or at least let people pay a one time fee for some exception) anyway, since we already have certificate transparency, we could have a similar one to look up MT…
Reputation isn't public because then spammers game it and you get worse filtering outcomes. ISPs learned this the hard way.