This helps ensure that you're not blocking the empty address. Blocking it means that you won't get bounces. It issues RCPT TO the address used in the envelope sender of the test initiation mail. It issues a DATA command and throws down a small piece of test mail. If one of these commands fails, the spamblock is working.
Some people implement their spamblock so that the mail is accepted and dropped on the floor.
As far as I can tell, the email was delivered. That might not be what you want. This method of spamblocking is probably not a good idea, because it's better to let a spammer know that their mail isn't getting through. It will discourage them, and that's a good thing. The entire SMTP dialogue is emailed back to the envelope sender address.