If you mean self-hosting email, then good luck.

It’s a lottery with the IP and even the IP space you get, whether anyone will actually receive your emails.

I hosted my own for a few years, but god fed up telling everyone to dig through their junk folder for my emails, and not being responded to very often, probably because of just that.

Maybe some providers have it better, but I tried a few and each was just not good. I really think Microsoft, Amazon, Google and other big players have intentionally separated the good, trusted IPs, ones they use for email services specifically, and made the other worse