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.
Ngl, I can't blame most for flocking to Gmail. It's a lot more of a pain in the rear to self-host something like that, and it's just plain convenient.
It's the same reason a lot of the people leaving Gmail go to essentially the Privacy Google (Proton) as the replacement.