I think email only proved the need for strong moderation in the case where the expectation is that you can send any message to anyone with only knowing their ad

I think email only proved the need for strong moderation in the case where the expectation is that you can send any message to anyone with only knowing their address. If there were a standard for strictly formatted "introductions", which were the only type of message you could send someone unless you were in their address book (and had confirmed public keys out of band?), then spam probably wouldn't be profitable enough to exist.