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.
That was the theory, nowadays moest email goes from google or microsoft to google or microsoft. At least 99% of the rest goes directly from the senders provider to the recipients provider. Afaik none of the larger providers still accept non-TLS connections.