Incoming Blacklist Filtering Rules
In the Incoming Blacklist Filtering Rules page you can view all blacklist filtering rules that have been set up for your domain(s) 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).
Unfortunately, the Technical Support team is unable to support any customization of the predefined Rulesets or those you build yourself.
Due to the potential complexity in building a regex pattern, we advise that only users with regex experience should attempt to create new rules or customize existing ones.
You can access this page at the Admin Level and the Domain Level.
You can also set up Blacklist filtering rules for outbound mail - see Outgoing Blacklist Filtering Rules.