I self-hosted for 25 years. My SMTP server is at Hetzner for the last 15 years.

I was probably lucky, but I rarely had delivery problems. The last one was a couple years ago with Microsoft swallowing my emails and it was due to the combination of a fairly old exim and a TLS certificate verification quirk at *.protection.outlook.com. I found a fix in the form of a configuration option somewhere on SO.

I must admit that when I send a really important email, I check the mail server log if it went off without errors, but this does not bother me as checking logs manually once in a while is a good thing anyway.