There are plenty efficient rbl lists that are transparent. There's grey listing. It's not like "today, you feel white-ish enough to not be silently dropped at

There are plenty efficient rbl lists that are transparent. There's grey listing. It's not like "today, you feel white-ish enough to not be silently dropped at gw, black-ish enough to go in the spam folder without warning" is the only valid policy to fight spam. Even simply rejecting with an error (spam suspected) would be better than the silent treatment. And I don't see anything wrong with telling people how you set up a firewall. We even write books about that.