While reviewing security policies, a company's IT administrator realizes that they need to improve the way they protect confidential emails being sent outside the organization. What method should the administrator recommend to ensure both the confidentiality and integrity of the emails?
Implement email encryption and require digital signatures.
Enforce a policy of two-factor authentication for email account access.
Schedule regular data backups of all email correspondence.
Restrict email communications to internal servers only, barring all external communication.