Earlier quoted context omitted.
I think ironsides was referring to sending email, not receiving it. Sending email from a mail server without a good reputation can often land your email in spam filters these days. It's all very well saying that the amount of spam you get is manageable, but that doesn't really matter if your own outgoing email becomes unreliable because you aren't using a recognised provider.
Jim, what can we do to increase the odds of our email reaching the intended destination on self-hosted domains?
1) have a valid PTR record for the email server.
2) Set up SPF records.
3) Just run email on it. If you do run a webserver on the same server, DON'T RUN PHP! In my experience [1] the single most abused attack vector on webservers is PHP and about 60% of the time it's abused to install spam sending software on the server and that leads to the IP address getting marked as a spammer.
[1] About fifteen years in web-hosting.