Use the Sender Reputation feature to collect information about recent e-mail messages received from individuals and domains. ...

Use the Sender Reputation feature to collect information about recent e-mail messages received from individuals and domains. If a sender appears to be the source of junk e-mail, the sender's address is added to the list of blocked IP addresses. You can enable and disable open proxy testing. You can also set the threshold for blocking a sender and how long to block the sender.