I have never had a problem sending to gmail or Microsoft addresses that didn’t involve at least making it to the spam box. I can’t speak with absolute certainty how every email admin handles things, but I have run into issues sending mail to some domains where I got a bounce and was able to reach out to the admins and get it corrected. Accepting mail for delivery but failing to deliver must be a violation of some RFC or email standard as it makes it impossible to send mail as a non-megacorp.

What I would like to get across is that self hosting is not impossible or unacceptably unreliable. If Google and Microsoft have policies that make it difficult to send messages to gmail or hotmail users, that isn’t a reason in and of itself that we should not self host. It’s a reason that we should work with Google/Microsoft to have better policies - but accepting things as they are and writing off self hosting as impossible is eventually accepting control of email by a limited handful of corporations, which I don’t think is a good thing.