CompTIA Security+ All-in-One Exam Guide (Exam SY0-301), 3rd Edition, 3rd Edition

Security of E-Mail

E-mail started with mailbox programs on early time-sharing machines, allowing researchers to leave messages for others using the same machine. The first intermachine e-mail was sent in 1972, and a new era in person-to-person communication was launched. E-mail proliferated, but it remained unsecured, only partly because most e-mail is sent in plaintext, providing no privacy in its default form. Current e-mail is not much different from its earlier versions; it’s still a simple way to send a relatively short text message to another user. Users’ dependence on e-mail has grown with the number of people accessing the Internet.

Internet e-mail depends on three primary protocols, SMTP, POP3, and IMAP. Simple Mail Transfer Protocol ...