Personally, I find the most realistic use case for self hosted email is service email.

The user is actively seeking the email, spam filters won't matter, and its easier to get out of spam once other email providers recognize its a legit service.

I host email on a Hetzner dedicated server, and it arrives in inbox on gmail, not Outlook though.

But that didn't affect anyone really, its OK.

I use postal, but Maddy looks interesting.