Emai system funtioningR.G. IyerHave you ever wondered how email system works technically? Here is a detailed study about
email. You can details of how email is received, how email is sent and it's stored. Your e-mail client allows you to add
attachments to e-mail
messages you send, and also lets you save attachments from messages that you receive. Attachments might include word processing documents, spreadsheets, sound files, snapshots and pieces of software. Usually, an attachment is not text (if it were, you would simply include it in the body of the message). Since e-mail messages can contain only text information, and attachments are not text, there is a problem that needs to be solved. The recipient would then save the uuencoded portion of the message to a file and run uudecode on it to translate it back to binary. The word "reports" in the first line tells uudecode what to name the output file. Modern e-mail clients are doing exactly the same thing, but they run uuencode and uudecode for you automatically. If you look at a raw e-mail file that contains attachments, you'll find that the attachment is represented in the same uuencoded text format shown above! Considering its tremendous impact on society, having forever changed the way we communicate, today's e-mail system is one of the simplest things ever devised! There are parts of the system, like the routing rules in sendmail, that get complicated, but the basic system is incredibly straightforward. The next time you send an e-mail, you'll know exactly how it's getting to its destination! The Real E-mail SystemFor the vast majority of people right now, the real 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 a POP3 Server, where POP stands for Post Office Protocol. The POP3 server handles incoming mail. A typical e-mail server looks like this: The SMTP server listens on well-known port number 25, while POP3 listens on port 110mail ClientsYou have probably already received several e-mail messages today. To look at them, you use some sort of e-mail client. Many people use well-known stand-alone clients like Microsoft Outlook, Outlook Express, Eudora or Pegasus. People who subscribe to free e-mail services like Hotmail or Yahoo use an e-mail client that appears in a Web page. If you are an AOL customer, you use AOL's e-mail reader. No matter which type of client you are using, it generally does four things: ·· It shows you a list of all of the messages in your mailbox by displaying the message headers. The header shows you who sent the mail, the subject of the mail and may also show the time and date of the message and the message size. It lets you select a message header and read the body of the e-mail message. It lets you create new messages and send them. You type in the e-mail address of the recipient and the subject for the message, and then type the body of the message. Most e-mail clients also let you add attachments to messages you send and save the attachments from messages you receive. Sophisticated e-mail clients may have all sorts of bells and whistles, but at the core, this is all that an e-mail client does