This makes running your own mail server so hard that it is nearly impossible (that is, if you care about people actually receiving the email you send them):
https://pluralistic.net/2021/10/10/dead-letters/
What's interesting about enshittified email is that it didn't start with corporate takeover: it started with volunteer-maintained blocklists of untrustworthy servers that most email operators subscribed to, defederating from any server that appeared on the list.
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