Question:
E-mail - What is it and how does it really work?
Answer:
(Borrowed from howstuffworks)
Have you ever wondered how e-mail gets from your desktop to a friend halfway around the world? What is a POP3 server, and how does it hold your mail? The answers may surprise you, because it turns out that e-mail is an incredibly simple system at its core. In this article, we'll take a look at e-mail and how it works.
An E-mail Message
An e-mail message has always been nothing more than a simple text message -- a piece of text sent to a recipient. In the beginning and even today, e-mail messages tend to be short pieces of text, although the ability to add attachments now makes many e-mail messages quite long. Even with attachments, however, e-mail messages continue to be text messages.
The E-mail System
Given that you have an e-mail client on your machine (like Microsoft Outlook, Eudora, or Pegasus), you are ready to send and receive e-mail. All that you need is an e-mail server for the client to connect to.
We know that machines on the Internet can run software applications that act as servers . There are Web servers, FTP servers, telnet servers and e-mail servers running on millions of machines on the Internet right now. These applications run all the time on the server machine and they listen to specific ports, waiting for people or programs to attach to the port.
For the vast majority of people right now, the e-mail system consists of two different servers running on a server machine. One is called the SMTP server, where SMTP stands for Simple Mail Transfer Protocol. The SMTP server handles outgoing mail. The other is either a POP3 server or an IMAP server, both of which handle incoming mail. POP stands for Post Office Protocol, and IMAP stands for Internet Mail Access Protocol. A typical e-mail server looks like this... |