Legitimate bulk email is not a thing you want to have decentralized - the anti-spam efforts of the past 20 years or so have made that all but impossible.
To get good results on your own server, you need:
(a) To be sending email that people want to receive.
(b) To have the technology setup correctly. It's not hard; we do it all the time for our clients.
(c) It's greatly beneficial to above ~20k messages/day on your own server. Not required, but being above that point lets the ISPs gather statistical data on your complaint and open rates, which allows reputation filters to click in.