End-to-end encryption ensures that email content is encrypted during transmission and can only be decrypted by the intended recipient. This approach provides robust protection against interception and unauthorized access. Encryption of Corporate Network Traffic (Option A):This does not address email confidentiality once the email leaves the corporate network. Complex User Passwords (Option B):Enhances account security but does not ensure email confidentiality in transit. Digital Signatures (Option D):Ensures authenticity and integrity but does not encrypt the email content. Reference:ISACA CISA Review Manual, Job Practice Area 4: Protection of Information Assets.