Good counterpoint, and to add, Gmail itself is more than happy to throw any email into spam if it isn't from a major provider. I had this happen with my own domain email, and even after telling Gmail the email is legit, it still spam filters it.
Plus, guess what email provider HR often uses but shouldn't... That domain isn't Gmail but you better believe their boss paid the 6 dollars a head to get them a gsuite portal with Gmail Spam filters.