IP reputation is done by everyone doing email who aren't tiny, in both directions. The large players really aren't doing anything special. It's just frequency

IP reputation is done by everyone doing email who aren't tiny, in both directions. The large players really aren't doing anything special. It's just frequency bias, because you want to deliver to them. It's also a full-time affair only if you're trying to deliver content people don't want. Yes it takes some effort in all cases because you can't just go on and start blasting, but it's not a full-time effort with those providers.