SPF dkim and dmarc aren't exclusive to ipv6. I think what the author is bemoaning is just how exhaustive the requirements are to send to one of googles cloiste

SPF dkim and dmarc aren't exclusive to ipv6. I think what the author is bemoaning is just how exhaustive the requirements are to send to one of googles cloistered mailservers in the first place. check senderbase and the rbls, you might be there too if you're on a less gilded cloud provider like oracle or ibm. in general new mailservers take some TLC to repair the IP space you're given before providers will trust it.