This document discusses email security and the threats posed by unauthorized access and modification of emails. It outlines common threats like message interception, modification, false messages, and replay attacks. It emphasizes the importance of confidentiality, integrity, and availability for secure email. The document recommends steps for security at the sender's side like using incognito mode and avoiding public computers. It also suggests checking email headers and avoiding unknown attachments for security at the receiver's side. Finally, it describes PGP and S/MIME as methods for securely transmitting emails through encryption.