White-list email domains
You can define a list of comma-separated email domains such that the system allows sending emails to only those domains. Outgoing emails to any other domain i.e. other than those listed will be prohibited.
Procedure:
Login to the system and select PC from the product navigator.
Under the General Configuration section → Email Gateway → Enable Outgoing Domain Whitelisting.
Provide a list of email domains to be white-listed. Separate them with commas.
Click on Save.