Administrators of enterprise and business tier accounts can customize the email headers to suppress the exposure of the email addresses for CC'd parties and additional recipients.
By default, the setting is disabled, and the email addresses of any CC'd party and/or additional recipients can be read from the email headers.
Enabling the Hide the other recipient's addresses from all emails option eliminates the CC email and any additional participant email addresses typically included in the email header.
Example when the setting is disabled:
Example when the setting is enabled:
The option to suppress the exposure of email addresses can be enabled in enterprise and business tier accounts at the account and group levels.
The controls can be accessed by navigating to Account Settings > Email Settings > Customize To and CC fields: