What on earth is an email server?

Answer 1

An email (or "mail") server is the computerized equivalent of your neighborhood mailman. Every email you send passes through a series of mail servers on its way to the recipient. Although it may seem that email is sent instantaneously (or nearly so), the reality is that a complex series of transfers through these digital mailmen takes place. Without them, you would only be able to send emails to people whose email address matched your own. For example, if you have a gmail email address, you would only be able to email other people who had gmail, not anyone using hotmail or Yahoo.