Messages sent from these addresses receive a detrimental score
Including an address on this black list does not automatically guarantee that a message from that address will be considered spam. Instead, messages from the black listed addresses will have the amount specified on the Spam Filter screen added to their spam scores. For example, if you have the spam score threshold set to 5.0 and the black list value on the spam filter screen set to 50, and a particularly low-scoring message arrives that gets a spam score of -50.0 or lower before the black list value is added, then the final spam score of the message will be less than 5.0, thus denoting it as a legitimate non-spam message. This would rarely happen, however, because messages rarely have that much subtracted from their spam scores unless they contain some other special element, such as a white listed address.
This screen is unavailable when you have configured MDaemon to use another server's MDaemon Spam Daemon (MDSpamD) for Spam Filter processing. This Spam Filter list will be maintained on the other server. See Spam Daemon for more information.