Actually to be fair, mine works fine and always has. The final boss is making Hotmail/live/Microsoft actually accept your email despite you jumping through all the hoops to have perfect spam score.
Everyone keeps saying that but I just can't see it. The only time my mails were rejected was because I didn't know what I was doing at the beginning of my journey. Now, whenever I changed my stack or did some major updates the past 20 years or so, I just go to 2-3 sites that analyze my mail server from the outside and tell me if there is anything wrong. The free tier is always more than enough.
Just make sure there is at least one service in the list where you send an email to a generated mailbox and have it analyzed. Just looking at the mail server is not enough to find all potential configuration issues.
I aim at a100% score. It's time consuming the first time around but later it's just a breeze.
Mine also works fine though. That being said I do only apply for jobs using this email so if you have a problem with hosted email providers I probably don't want to work for the company anyway.
IMHO, as someone running his own mail server, the real final boss is LDAP and implementing SSO on all your selfhosted goodies. Bonus points if you then use it to login to other services that support OAuth 2.0.
I have my own mailserver just for me and it wasn't that complicated to be honest. I set it up with Mailcow in Docker in under a day. So far it has been stable with regular backups and updates through Lighthouse.
Maintenance comes down to 5 minutes every three months because somehow Let's Encrypt and Mailcow don't like each other and I have to renew the certificate manually.