Which of the following would work BEST to improve the likelihood of employees quickly recognizing fraudulent emails?

A finance department employee has received a message that appears to have been sent from the Chief Financial Officer (CFO) asking the employee to perform a wife transfer Analysis of the email shows the message came from an external source and is fraudulent.

Which of the following would work BEST to improve the likelihood of employees quickly recognizing fraudulent emails?
A . Implementing a sandboxing solution for viewing emails and attachments
B . Limiting email from the finance department to recipients on a pre-approved whitelist
C . Configuring email client settings to display all messages in plaintext when read
D . Adding a banner to incoming messages that identifies the messages as external

Answer: D