Solution
2. In the "Security & Filtering" context open the "Additional AntiSpam Methods" page
3. In the "DNSBL" section, click the "Add DNS Blacklist" button.
4. Provide a name for the Blacklist (the name of the provider is recommended).
5. Enter the black list operator's DNS server, or the provided settings to query the blacklist (for example: bl.operator.tld).
6. Click the "Quick Add" button.
7. Click the "Save Configuration" button to make the changes permanent.
NOTE: You can set up exceptions for the blacklist look-ups using the "Add IP/Range" button below the blacklist definition area.
NOTE: This rule will not be applied for authenticated users.