Just rent a server with a good company (such as Hetzner) that’s likely to have clean IPs, install Linux and Postfix, and Dovecot if you want IMAP access, read and carefully follow the Postfix documentation, read any of many online guides for setting up DKIM, etc., and you’re good. Once up, it’s largely hands-off. Mine has been running smoothly for over a decade. Don’t believe the FUD.