When we receive a response back on one of your email campaigns, we process and forward those on to you, based on a number of rules in your account Settings. We have just updated the spam detection for response emails we receive so we can prevent forwarding spam responses to you as much as we possibly can. How? We implemented a Spam Assassin filter to clean out the spam. Emails that are most obviously spam will now be rejected. Thus you'll be happy not to be receiving such email in your inbox anymore.
Note: You can manage your reply settings under Settings —> Reply Management —> Reply Handling