Blacklist

Blacklisting allows you to prevent some e-mail addresses or domains from sending e-mails to you or your users.

The Blacklist can be applied by two levels of management: the Administrator and the User

The User applied preference always overrides the Administrator set preference. If there is no User defined preference, the Administrator one takes full effect. If for your domain, the Administrator decides to whitelist the domain gmail.com but a User creates a Blacklist rule for that domain, e-mails from gmail.com will be blocked for that user