@aral @cancel all that being true, if email had opt-in for receiving email (aka 'follow') my inbox would be spam free. And the moving goalposts of DKIM & SPF records & mail server IP reputation etc that were added to try deal with spam/filters and allowed the monopolies to squash competitors, wouldn't be needed.

(Which isn't to say the fediverse doesn't have big centralisation vulnerabilities say around caching/media storage/notifications etc - but more that not all monopoly risks are the same)