Email does rely on IP reputation as a major component in deciding if something is spam. The system has matured to a point where it works fairly well and transparently ... but the consequence has been you can't reliably send from an IP block unless somebody is very actively handling abuse and working with the reputation services to keep their IP space in the internet's good graces.

But: I wouldn't want to allowlist based just on one reputation service. I've got some ideas on how to handle spam for my instances involving a few different datapoints. This could be useful as one, if it ends up with enough data.