Handling of non-deliverable emails

Please note that is a major feature of this behavior is that SpamFilter will never send a non-delivery email for each email that is rejected. instead, this task is delegated to the remote server. This is very, very important, as some other anti spam products send themselves a non-delivery email back to the sender for each spam email that is stopped. This means that your network would be the source of potentially hundreds of thousands of non-delivery spam emails, one for every spam email you receive. This would cause your own network to become blacklisted by many other anti spam providers as you would be essentially a source of spam.