> Anyone: correct me if I'm wrong.

OK: it's easy, unless you're the "atechnical" sort.

Is it recommended? I'm torn here, because the big beasts are systematically spam/junk-classifying and even rejecting e-mail sent from independent MXes despite ticking the right checkboxes (FQrDNS, SPF, DKIM, DMARC) and having a clean IP-address in a tidy network.