The worst part really is just getting off the damn spam lists. There is almost no documentation anywhere for do's and dont's. I ultimately had to setup a sending relay for the mail on my status monitoring VPS because my residential IP triggered most spam filters, but I only found out that that was the problem from forum posts investigating the same problem. I check with stuff like mail-tester, get back perfect scores and yet most of my outgoing emails have a good chance to land in the spam folder anyway (but at least they get delivered so that's a plus I guess)
As others in other threads have said: Google and Microsoft have killed the ability to self-host email simply by black-boxing their spam filters. As a user you have no real way to fix your mail server such that your emails get delivered into the inbox reliably.
Must've been one powerful curse... that or the little guy over here is already influenced by Hartmut et co. and will turn into a devout follower of St. Rozemyne