I'm sending through a vps and have properly set up all the things (dmarc, dkim, spf, et al).

It was years ago when I set up, but I spent some time trying to get the mail to go through (wife uses Hotmail). The rabbit hole led me to a service I could purchase that would allow the mail to go through. Many fora articles paralleled my own experiences.

I don't send spam, and my "reputation" is good. I'll look into it again.