Encryption allows e-mail traffic to be transmitted so that only __________.

Encryption is a crucial security measure in communication, particularly for protecting the content of emails. When email traffic is encrypted, it transforms the original message into a format that is unreadable to anyone who does not have the proper decryption key. This ensures that only specific individuals – namely, the sender and the intended recipient – can access and interpret the content of the email.

This mechanism is fundamental to maintaining confidentiality and protecting sensitive information from unauthorized access. It directly supports the principle of privacy in communications, guaranteeing that the details contained within the email remain secure against eavesdroppers or any third parties. This is why the correct understanding is that encryption ensures only the sender and the designated receiver are privy to the content of the message.

In contrast, other options imply broader access or visibility to additional parties, which contradicts the primary purpose of encryption in preserving confidentiality.