What is required for an EMTA to receive an authorization key for telephone service?

For an EMTA (Embedded Multimedia Terminal Adapter) to receive an authorization key for telephone service, it is essential that the MAC address is assigned to a customer account in the billing system. This requirement ensures that the specific device is recognized and authorized by the service provider for use on the network. The MAC address uniquely identifies the device, allowing the provider to manage and verify its compatibility and association with the customer's account.

When the MAC address is properly linked to the customer’s account, it facilitates the activation process, ensuring that the service can be seamlessly delivered to that particular device. This authorization step is crucial in maintaining the integrity and security of the telecommunications service, as it helps prevent unauthorized access to the network.

The other options involve aspects of service integrity and account status, but they do not directly address the primary requirement for receiving the authorization key; thus, they represent additional but less critical factors in the process.