A company recently suffered a breach in which an attacker was able to access the internal mail servers and directly access several user inboxes. A large number of email messages were later posted online. Which of the following would best prevent email contents from being released should another breach occur?


A. Implement S/MIME to encrypt the emails at rest.
B. Enable full disk encryption on the mail servers.
C. Use digital certificates when accessing email via the web.
D. Configure web traffic to only use TLS-enabled channels.