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.