You can add the user to /etc/virtual/blacklist_usernames to prevent them from sending emails. For more information about this, please refer to https://help.directadmin.com/item.php?id=655
You can add the user to /etc/virtual/blacklist_usernames to prevent them from sending emails. For more information about this, please refer to https://help.directadmin.com/item.php?id=655