Chapter Four introduced the concepts of communicating online. One method of online communications is electronic mail or email. Email is a system in which you can compose a message using your laptop, computer or smartphone and that message is sent through various networks to reach the intended email recipient. The advantages to email over regular mail are clear. Email is fast, low-cost, convenient, and easily managed. Further, email is accessible through any device that is configured to receive email such as your laptop, computer, or smartphone.
There are several components to an email system. Each email recipient must have their own unique address on a server. This is called a user ID. The user ID is comprised of a unique identifier for a person. Most often, it is the recipients name but sometimes people will create a user ID that they creatively generate. In addition to the user ID, there is a host name. The host is the server where the email service and recipient's account resides. The user ID and the host name is separated by the @ symbol. The final piece of an individual's email address is the top-level domain. A top-level domain identifies something about the website such as its purpose, the organization that owns it or the geographical area where it originates. The top-level domain follows the host name and is preceded by the period in the email address. The person who generates the email enters the email address when they create the message just as a person would address an envelope to identify their intended mail recipient.
There are several steps in the creation and delivery of an email message. In order to use email, users must have access to an email client which is a program that is used to create, send, and receive email. Email clients are installed on your computer. Next are email servers and protocols. The outgoing mail server determines the best route to deliver the email message to the recipient. The Internet Service Provider's (ISP) incoming mail server receives the message and places it in the recipients inbox.
A protocol is a standard method used at each end of a communication channel in order to properly transmit information. The email client and email server exchange information with each other using an established protocol. The email message is transmitted over the internet using the packet-switching and TCP/IP technology that govern all communications over the internet. The recipients email server and email client exchange information with each other using an established protocol. There are a variety of protocols that can be used. They are as follows:
IMAP (Internet Message Access Protocol) is a standard protocol for accessing email from your local server. IMAP is a protocol in which email is received and held for you by your ISP's server. IMAP requires only a small data transfer so this works well even over a slow connection such as a modem. Only specific email messages requested will be downloaded from the server.
POP (Post Office Protocol) provides a simple, standardized way for users to access mailboxes and download messages to their computers. When POP protocol is used, all your email messages will be downloaded from the email server to your laptop or PC. You can choose to leave copies of your emails on the server as well. The advantage is that once your messages are downloaded, you can terminate the internet connection and read your email without incurring further communication costs.
The SMTP (Simple Mail Transfer Protocol) is used by the email server to deliver your email to the recipient's email server. The SMTP protocol can only be used to send emails, not to receive them. The outgoing SMTP server contacts the Domain Name System (DNS) to identify the host domain name of the email address and determine the best route to send the message.
The HTTP protocol is not a protocol dedicated to email communications but it can be used for accessing your mailbox. Also called web-based mail, this protocol can be used to compose or retrieve emails from your account. Hotmail is an example of using HTTP as an email protocol.
Shown below is the life-cycle of an email message:
I like this illustration because it pretty clearly demonstrates in the first section, my understanding of email transactions prior to reading this chapter! As you can see, it is much more complex that it looks to the email user.
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