sentences:  By means of some available tools, persons other than the designated recipients can read the email contents.Email encryption can rely on public-key cryptography, in which users can each publish a public key that others can use to encrypt messages to them, while keeping secret a private key they can use to decrypt such messages or to digitally encrypt and sign messages they send.With the original design of email protocol, the communication between email servers was plain text, which posed a huge security risk.