I think the timeline is critical here and should be highlighted. Self hosting email server was something that worked out just fine in the past (used to host until 2014), however things have changed a lot with the scale of abuse. its not worth it unless you are doing it as a business. Sending a email from your home IP to big email providers with reliability is next to impossible. Even if we discount the spam management,

1. IP reputation is a big deal, its not just about not being on some blocklist, call it a cartel at this point, its about being on the allow list for other mail providers

2. Keeping it reputable is a continuous effort

The importance of IP reputation is a reason for why email isn't using IPv6 much.