When a case is submitted to AWS Support, through the Amazon Chime Console or AWS Support Center directly, update emails are sent only to contacts added at the time of case creation. Additional contacts cannot be added after the case has been created.
Customers with paid Support can associate any contact with a case via the Additional contacts box.
Additional contacts. Provide the email addresses of people to be notified when the status of the case changes. If you're signed in as an IAM user, include your own email address. If you're signed in with your email address and password, you don't need to include your email address in this box.
Customers with Basic Support can associate only existing account contacts with a case.
Note If you have the Basic support plan, the Additional contacts box isn't available. However, the Operational contact specified in the Alternate Contacts section of the My Account page receives copies of the case correspondence, but only for the specific case types of Account, Billing, and Technical.
For more information, visit Getting Started with AWS Support - Case Management in the AWS Support User Guide.