See Blocked Senders List

Lists of IP addresses that are being used by or belong to organizations or individuals that have been identified as sending Spam. Blacklists are often used by organizations and Internet Service Providers as part of their filtering process to block all incoming mail form a particular IP address (or block of addresses).

Lists of domains and IP addresses that have been reported or accused of sending spam. The deliverability team at IntelliContact works every day to minimize the impact of blacklists on our customers.