Like many great computing concepts, email--electronic mail--was first introduced in the 1960s, though it looked much different then. A thorough history of email, while certainly a great technical curiosity, is beyond the scope of our purposes here, but I think it would be helpful to take a look at a few of the email protocols still relevant today, those being SMTP for sending mail, and POP3 and IMAP for (from your email client's perspective) receiving mail. (Technically, the email is received by the server via SMTP as that is the on-the-wire protocol used by Mail Transfer Agents (MTAs), to transfer mail from one server to another. We non-MTA authors never think of it in those terms, so we need not be overly concerned by that distinction).
We'll start with sending an email, as our focus in this chapter will be more on folder management. SMTP (Simple Mail Transport Protocol), created in 1982 and last updated in 1998, is the dominant protocol to...