Honestly we should just do this. Maddy and Stalwart have cheap enough concurrency and good enough scalability they could easily delay SMTP accepts server side for a time delay based on a combination of a local and global heuristic. We could easily start to produce an auditable global heuristic as well and start prototyping the solution today. Over time the community will have to decide how to work with the Cabal, or more specifically the Cabal will have to learn to start to re-engage with the community.

Just start.