It is possible that this isn’t deliberate on their part. (Yes, yes, I know.) Technically if enough people reported a sender as spam they would be classified as a spammer on various antispam lists.
That said... if you’re using free mail services, guess what? The provider sets the rules and there’s f*** all you can do about it. “If you’re not paying for the product, *you* are the product!”
Oh, okay. Then it’s perfectly fine then that I hang this “We Reserve The Right To Refuse Service To Anyone” sign on the door of my bakery shop? Asking for a friend.