I know of some small servers that get a lot of spam and hacking attempts, and their most effective tool against abuse is an IPv4 block ban. Increasingly this be

I know of some small servers that get a lot of spam and hacking attempts, and their most effective tool against abuse is an IPv4 block ban. Increasingly this became more and more difficult, and I assume email servers are at the same point. Thanks to VPNs, people appear to be able to spawn insane numbers of random IPs. One solution this decentralized server system came up with is the concept of accounts that have some barrier to entry to create (which involves a delay and proving identity). This account has a private key and it uses this to access the servers through any IP. Abuse on this account and any connected accounts of course leads to the key being temporarily revoked. Lots of positive interactions with well established accounts increases your credibility. Lots of reports decreases you credibility. If you have been sending credible emails with multiple hosts for 10 years, even if you did get flagged, you would be given the benefit of the doubt. Hell, it should be easy to email the host and give them the headers and the reason why the email was flagged. About the email space now being owned by big tech, it could simply be time for a boycott until they improve their practices. There is far too much centralization on the web now, and we all contribute to it every time we use an external service rather than host our own.