This is a key difference. Many people who have a bad time self-hosting mail set up with a minimum-effort major provider like Hetzner or DO — you're guaranteed to have spammers as neighbours some of the time, and other networks will behave accordingly when deciding whether to accept your mail.
A real server in a proper datacentre is great — I do the same — but as a lower-cost option a virtual server with a small, clueful provider who knows their customers also works just as well.