Yes, sadly they are legitimate emails so its hard to block them. The problem seems to be on zendesk side where they are accepting any email as the source of the ticket and simply replying to that email with the contents of the ticket.
Apparently they are well aware of this problem since at least last year:
Apparently they are well aware of this problem since at least last year:
https://support.zendesk.com/hc/en-us/articles/9833274501786-...