@tinselpar@sdx I disagree. I've been self-hosting my email since 1998. I routinely end up on blacklists and low-reputation IP lists and other situations that limit my email from reaching people.
The big players like gmail, outlook, yahoo have absolutely no method of appeal or explanation. You can submit to an opaque form and maybe email starts getting delivered again. But you'll never get a reason or even a notification that they made a change. It is a constant labour: So much so that I pay a monitoring service to alert me if my server ends up on a list somewhere.
Look at paco.to and look for issues. It's "right" in terms of SMTP standards and compliance. This stuff happens to me ALL THE TIME.
I was emailing my local government office and had to call them to find out why they weren't replying. All my mail was going into a junk folder for no reason that I could see or control.
When big players adopt something, small players must also, or we lose the ability to send email to massive numbers of people.
So while it is "possible" to run your own small email server, the dominance of a few absolutely massive players makes it a lot of work for the small operator.