DKIM, DMARC, SPF, rDNS/PTR, EHLO... all correct and verified in the email "original source," BY GOOGLE. Still goes to SPAM folder because **** you, apparently. I hate Google.
If you want you can PM me your dkim and dmarc and SPF policy. Or just send me your url and I'll look it up. I used to fix these for a living. It's likely an issue with your SPF not being properly annotated.