I have used Mailinabox on a Hetzner server for about an year. My email delivers to all the major providers. However, small providers will occasionally block my email. So I continue to use my Gmail address for now.

With small amounts of evidence, I think if my contacts on those providers email me first, and I reply to those emails, then my domain is not blocked.

server4you.

there is one blocklist im aware of that simply categorically blocks all their IPs, but thankfully none of the "big tech" players use it, so its really of no consequence to me