I run several small business email systems in the UK. You do need to get at least SPF and the usual MX, A and PTR records sorted at a minimum. Also A and PTR

I run several small business email systems in the UK. You do need to get at least SPF and the usual MX, A and PTR records sorted at a minimum. Also A and PTR and (E)HELO must agree. You can relay your mail via another service if you need to gather some karma for your domain but ensure you get your DNS records right. That way you can run your own full mail system from a "dodgy" IP address. It's not for everyone but neither is IT in general. If you can fathom a Mastodon server then you can manage an email system - technically speaking. However, you must get the basics sorted out and don't send anything that can be construed as spam!