I "solved" this for email years ago (as did many before me):

https://blog.nawaz.org/posts/2018/Sep/solving-my-email-probl...

Any communication channel that doesn't involve a whitelist (e.g. invite/approve) will have this problem. Email. Phones. Text messages.

If you want to fix this, the protocol must ensure the recipient first agrees to communicate with you. Until they do, all messages to them will be automatically blocked.

This solution works. Yes, there are always ways to get around it, but in practice, it cuts the nonsense by well over 90%.