I've seen the controversy where myisp.com blocked mail from 2 email hosts. So since there is no one big owner what is stopping someone creating an email host that propagates CP or other illegal stuff?

From what it seems like is ISPs can try to block from those hosts but the only justice that can happen seems only from government/police but that only works in certain countries because more can just pop up bypassing the blocks.

I'm kinda concerned if this issue has no solution because it's a pretty sharp edge of the double edge sword of having instances anyone can create and host.

Because someone can just host a CP mailing list and now that list, even if blocked from other ISPs, still provides a safe space for pedophiles to share content and other illegal stuff.

Also what is stopping someone from creating an email host that has a slur for its name and then go sending email around to other ISPs. Like you don't want someone named "NAZI_LOVER@n-word.f-slur"

Adjust as appropriate for literally any other technology used on the Internet up to and including frickin' DNS.

ANY technology, without exception, has utility for evil as well as good. (Some are more evil-leaning, like corporate social media silos, while others are more good-leaning, like automated puppy scritchers, to be fair.) To pearl-clutch over one technology because it's the new one is just ...

... well, human I guess. Humans are always doing this shit.