1. Internal Use - Using Subusers to separate statistics or create accounts with different settings.
2. External Use, Unwhitelabeled Sending - If you are creating a Subuser to send messages on behalf of a new domain, you can either send on behalf of your current Whitelabel or you can purchase a new IP to Whitelabel a new Subdomain. Creating a Subuser that uses the parent account IP and Whitelabel results in a 'via' or 'on behalf of' message displaying in some email clients if you use a FROM domain that does not match the Whitelabeled domain. It is important to change the DKIM App settings for these Subuser accounts to match the parent account Whitelabeled sending domain.
3. External Use, Whitelabeled Sending - To send on behalf of a different domain and have the messages fully Whitelabeled, you need to purchase a new sending IP and Whitelabel that IP to the new sending IP. Please review our Creating & Whitelabeling A New Subuser To A New Domain article for more information.