I don’t know what you mean by “ethical”, but I use Sendgrid. They have a free tier that can send up to 100 emails a day.

Highly recommend. I moved my web hosting from my home server to a CPX11 server for better uptime (my tinkering around in the homelab was always bringing things down) and couldn’t be happier. It’s dirt cheap (cheaper than shared web hosting, even), performant (performance is better than shared web hosting) and reliable. With a 20TB bandwidth limit at the lowest tier, I can reverse proxy for most of my homelab, too.