They literally replied to his registered email and he has the reply. That would indicate that he has at least access to the account. So with OP’s next email quoting the reply ownership over the associated email address should be reasonably established.

I would like it if a community would remember the sorting I selected. Some communities I prefer to read sorted by newest. Others I like to read top last 12 hours.

It’s not, because they wouldn’t let me participate.