You can use seed list settings to configure a seed list, which is a group that receives a copy of the emails sent to your customers.
Contacts in your seed list include contacts (email address only) who are part of your organization, such as your customer support group. Contacts in your seed list receive all of the emails from your organization. They are useful to ensure mailing consistency and control.
To see these settings, go to Settings > Administration > Organization Settings > Seed List Settings.
Organization administrators can enable or disable the seed recipient and seed contact indicators in the subject line and message headers. Organization administrators use this option to the indicators if they believe they impede deliverability.