It’s funny when armchair experts insist that the fediverse won’t catch on because “federation is too hard to understand” when arguably the most widespread communication system on the internet follows the same model
Yeah and honestly, this is largely a reasonable standard for anyone running an email server. If you don’t have SPF, DKIM and DMARC, basically anyone can spoof your emails and you’d be none the wiser. It also makes spam much harder to send without well, sacrificing IP addresses to the many spam lists. I wouldn’t be surprised if some people setting up their own mail server were made aware of these things because of being blocked.