Which item is NOT required to encrypt an e-mail using PKI?

To successfully encrypt an email using Public Key Infrastructure (PKI), specific components are needed, and one of those is the requirement to facilitate the encryption process. An Internet connection is not an explicit requirement for the encryption itself because the encryption can be done locally. Once you have the necessary components such as encryption certificates installed on your email client, you can perform the encryption even without being connected to the Internet, as long as you have access to the public keys necessary for encrypting the message.

The other choices involve essential elements for the encryption process: a Common Access Card (CAC) is often used as a secure method for storing cryptographic keys, a CAC reader is necessary to access the information stored on the CAC, and having an email client configured for certificate revocation is important to ensure that the certificates being used are still valid and have not been revoked, which is vital for secure communication. Therefore, while all those components support the function of PKI encryption in different ways, an Internet connection itself is not necessary for the actual process of emailing an encrypted message.