Incoming Blacklist Filtering Rules - Domain Level
In the Incoming Blacklist Filtering Rules page you can view all blacklist filtering rules that have been set up for your domain's incoming mail and you can also add new ones. Incoming mail that matches any of the rules will always be blocked.
The rules are based on Python's regular expression (regex) syntax. (For more information on regular expressions, see regex101.com).
You can also access this page at the Admin Level for all of your managed domains.