The blacklist is a list of specific email addresses or domains considered to be associated with spam. Depending on your configuration, messages from these email addresses are automatically re-directed into a spam folder.
New addresses to block appear every day, which can make a blacklist difficult to maintain. To more effectively filter spam, use the Blacklist in conjunction with the Whitelist. A whitelist is a list of email addresses or domains which you have designated as legitimate email contacts. Messages from these contacts will not be blocked automatically and will be delivered successfully to your inbox.