Greenhouse Recruiting's Mark as Spam feature allows your organization to reject a candidate application from the Application Review process, mark the individual as spam, and automatically reject any future application from that email address.
From the Application Review page, navigate to the left-hand panel and click Mark as Spam.
Note: This feature is only available if your organization has configured the Spam rejection reason to be visible.
The candidate will be rejected, marked as spam, and any application from the email address used will be automatically rejected.
If you decide to remove the spam designation on the candidate, return to their profile and change their rejection reason to anything else to allow them to apply again!