You need to design a method to modify the current e-mail ordering system, which will be used until Fourth Coffee deploys the Web-based ordering application. Your solution must address business concerns and improve security. What should you do?

A.
Configure the mail server to disallow SMTP relaying.

B.
Instruct customers to obtain digital certificates from a trusted commercial certification authority (CA), and digitally sign all order e-mail messages. Reject unsigned order e-mail messages.

C.
Provide customers with a public encryption key, and instruct them to encrypt all order e-mail messages. Reject unencrypted e-mail messages.

D.
Implement an e-mail filtering solution, and add all customer e-mail addresses to the list of allowed addresses. Reject e- mail messages from other addresses.