Spam is REJECTED and not deleted. In cause of a possible false positive the sender (!) will receive a non delivery report. Deleted e-mails is always forbidden.
Peer (mailbox.org)
Peer (mailbox.org)
It is not exactly clear (on the website) what you mean by 'rejected', so the English text could be improved to make your meaning more explicit. Perhaps 'returned' would be better?
Good luck!
That's a big and very important difference.