@joeyh If Google is bouncing your email, check reverse DNS, SPF, DKIM, and DMARC, make sure they are all configured properly.
But the real problem is, when you have everything and Google starts accepting your mail, sometimes, it still flags your mails via IPv6 and moves it to the spam folder randomly.
And there's no incentive for Google to fix it, I guess, and we had to,
> limit mta for domain gmail.com inet4
But many companies use Gmail with their own domains...