I once went down a rabbit whole and discovered that Satoshi Nakamoto used a GMX email account, and it was still for a while before it was disabled. So, I am betting some admins at GMX in Germany may know more than the rest of us because this before end-to-end inscription of email was normal.

The other thing I was thinking is that it is much harder to be anonymous now than in the past because all the main email and social platforms try to authenticate your identity.