I ended up switching to Fastmail a few years ago, but before that I was relaying outgoing email through Amazon SES. It fixed all my deliverability problems. Before that, when sending from my own server, emails might just not show up. Not in recipient's spam folder, not rejected by their server. Accepted and then dropped mysteriously.

If I ever go back to self-hosting email, I would do the same except I would maintain a whitelist of friendly mail servers to which I would send directly. Or maybe just relay emails to Google/Microsoft via SES and send the rest directly.

> through Amazon SES. It fixed all my deliverability problems

How do you know? I have seen blocks of ip addrs blocklisted from AWS due to others abusing nearby ip addrs