We've had our servers blacklisted for "low traffic" and completely legit, authenticated emails marked as Spam. Completely new IPs with 100/100 reputation were blacklisted just because they were not known from before. To get us off from their lists we were in for a web of problems. It is all rigged against the small hosters. If you are a bigger one, you can just get directly in touch. I was personally all for the idea of running own mail servers, but after the experience so far, would say good luck with that. Unfortunate though.

I've had all kinds of problem with outlook.com and other Microsoft related email recipients marking my email as spam. I use Fastmail. Fine with Gmail though.