Electronic mail, popularly known as e-mail, is one of the most frequent applications of computer-based communications. It works on a store and forward principle. When a user prepares a message (usually off-line) and submits it for transmission, it is then sent along telephone (or similar) lines and received by the local message transfer agent - an e-mail service provider. The message header is analysed by special software to identify the recipient and his/her location. If the recipient is a local user then the message is delivered directly. Otherwise it is forwarded (posted) to the appropriate remote e-mail node, perhaps repeatedly through the network, until the message is delivered to the recipient's mailbox. This procedure can take from a few seconds to a few hours to send to anywhere in the world. On-line transmission is virtually instantaneous.
Early email systems were proprietary: private networks within companies or user networks which could not communicate with other systems. As the Internet developed, these email systems were modified so that you could send text messages to anyone with a similar system. Sending files or viewing HTML mail was (and often still is) problematic because these programs have proprietary mail formats, which limit their ability to communicate with other mail systems. As the Internet became a stronger force, new email standards were created to keep pace. Post Office Protocol, or POP for short, is an example; POP programs share a standard way of communicating, which means you can exchange mail (including attachments) easily with anyone on the Internet from their own computer (but not others). WebMail is the latest advance in electronic mail, allowing users to send and receive mail simply by using any web browser from any computer anywhere in the world.
mail programs are designed primarily for single computer use. Once you set up your email account by entering your POP3 and SMTP server names, you're stuck using that individual computer to send and receive mail.
Electronic mail can be used effectively for communication in a variety of situations: from international organizations with multiple remote constituents to internal office mail. The advantages of e-mail are: the originator of a message can take as much time in composing the message, but once the message is sent delivery is almost instantaneous; a message can be sent to one person or an entire mailing list with the same ease; e-mail received is easy to skim read and can be replied to instantaneously or after consideration at convenience; the costs are very competitive with postal charges, usually cheaper.
In 1996 it was estimated that there were more than 20 million people using e-mail for their day-to-day work.