They operate since 2007, they can track who is reliable and who is not. It's not like IPs change[1]. [1] yeah, they might be some people trying mail servers on

They operate since 2007, they can track who is reliable and who is not. It's not like IPs change[1]. [1] yeah, they might be some people trying mail servers on dynamic IP, but I'm not talking about those and Google would have some justification not categorizing them as reliable. I'm talking about using business level ISP offering with a static IP address and matching RevDNS.