Asterisks may be used as wild cards in the VIP list, but not in specific rules. Asterisks must appear before the @ symbol. For example, adding *@bademail.com to a VIP decline list would cause all email addresses from this domain to trigger a decline rule.
If an asterisk is used in an individual rule, such as a rule declining *@bademail.com, the rule would not trigger if fraudster@bademail.com (for example) was the email used in a transaction, because rule conditions require exact string value matches.