Email whitelist or blacklist
Email whitelist - An email whitelist is a list of IP addresses you define as acceptable for sending mail to your domain. Currently, this feature is available only in G Suite for Education. If you notice that legitimate emails from specific contacts incorrectly marked spam, you can whitelist the contact's IP address. After you whitelist the IP address, message originating from this IP will no longer be marked spam. Learn more
Email blacklist - An email blacklist is a list of email addresses you can block from sending mail to your domain. Administrators can block certain domains or users using the Blocked senders setting. In addition, users can create a filter in their individual mailbox to automatically send messages from specific users or email list to Trash. Users can also prompt our spam filters by reporting unwanted messages as spam.