All About E-mailBy Lawrence Abrams on January 17, 2007 | Last Updated: February 27, 2012 | Read 27,066 times.
Table of Contents
According to a report by The Radicati Group on May 9th, 2006, there about 171 billion e-mail messages sent daily, 1.1 billion e-mail users worldwide, and 1.4 billion active e-mail accounts. These numbers are staggering and truly reflect how e-mail has become such an important medium for communicating with friends, family, colleagues, and clients. Though so many of you use e-mail all the time, how many of you truly understand how e-mail works? This tutorial is designed to give an overview of how e-mail works as well as related e-mail features. Hopefully after reading this tutorial, you will be a more informed users and consumer of e-mail products or services. This is going to be a long and detailed tutorial so I suggest you print it out and read it casually so you can absorb it all.
When we think of e-mail most of us think of a program that we run on our computer such as Outlook, Outlook Express, Thunderbird, etc where we type a message, address it, press the Send button and expect the e-mail to get to our recipient. In this section I am going to explain what happens after we press the Send button. I will use the most widely used e-mail services, SMTP and POP3 as examples, but the concepts are essentially the same for all e-mail technologies
The current Internet email standard requires all emails to be sent as ascii, more commonly known as text. When you compose a message, format it, add any attachments and press the Send button, your e-mail software will automatically convert your message into a pure text format that your mail server understands. An example of what a message with a small attachment looks like after it has been converted to text is below. As you can see there are no images or other formatting, but rather only pure text.
Message Converted to Text
Once the e-mail has been converted to text, your mail software then sends the message to the outgoing mail server, or SMTP Server, you specified when you setup the mail account on your computer. When your outgoing mail server receives the e-mail, it examines the recipients, and uses DNS to determine where it needs to the send the message. It is important to remember that the mail server you send your initial message to does not know anything about the recipient. It only knows how to look up the IP address for a mail server that does know who your recipient is and send it there. Once your mail server knows what other server to send your message to, it opens a connection to that mail server and delivers the message. You can see how this is done in the figure below.
When the recipients e-mail server receives your e-mail message, it stores the message in the recipients mailbox which is located on the server. The next time the recipient checks for their e-mail, their mail client will connect to their configured incoming mail server, otherwise known as a POP3 server. If there is mail waiting for you, your mail client will request these messages from the POP3 server and start downloading them to your computer. As each message is downloaded, your mail client will convert the message from text back to its original format. These e-mail messages will now be visible for you to read in your Inbox folder of your mail software.
It is important to note that when you download a message from the POP3 server, and do not specify to leave mail on the server in your mail account settings, then the message will be downloaded to your computer and then deleted from the POP3 server. Therefore the only copy of this message will be on your computer, so make sure you don't need it before you delete it as there is no other copy elsewhere. An example of how POP3 works can be seen in the image below.
I am sure most of you know what attachments are, but for those who do not we are going to give a brief course on attachments and how they work. When you send an e-mail message you have the ability to attach a file, or multiple files, of any type to your e-mail message. When you send the message these attachments are sent along with it so that when the recipient receives the message they will see your attachments and be able to open them. By far the most common use of attachments are documents, such as word or excel docs, and pictures or images.
As most attachments are not text files and as the Internet e-mail standard requires all e-mail messages to be entirely text, your mail program will process the attachments in your mail message when you send them. It does this by converting each attachment into text and sending the message like that. When the message is downloaded by the recipient's mail program, the mail program will convert these attachments back into their original form so that you can open them properly.
Let's use the image below as an example to see how it would be transformed into text by a mail software.
When the mail software sends this message, instead of the sending the message purely as binary image, it instead converts it into text and sends it that way. The image above is converted to the following text:
When the recipient downloads the mail with the attachment, the e-mail software will automatically convert the attachment back to its original form. In this way mail programs can send multiple attachments and yet still follow the Internet e-mail standards of having all messages consist of only text.
In order to open an attachment you need to have a program installed on your computer that knows how to open that file type. If you do not, your operating system will give you an error asking which program you want to use to open the file. To get around this problem, make sure you have a program installed that can open the attachment you received. To determine what program you need to install, you first need to determine the file extension of the attachment. The file extension is the last part of a filename that starts with a period and has 3-4 letters after it. For example, a file named word.doc has an extension of .doc and a file named bleeping.gif has an extension of .gif. You can then visit a site like Filext.com and do a search for the extension. This site will then tell you what program you need to install in order to open the attachment.
Remember in the introduction we said that it has been reported that there is about 171 billion e-mails sent per day? A report issued by MessageLabs.com in November 2006 states that 74% of all e-mail is spam, that one in 137.5 e-mails contain a malware of some sort, and that one in 200 e-mails is a phishing attempt. That's right ... the majority of e-mail that is sent per day is useless unwanted trash that constantly fills our inbox. For those who do not understand what this means let me define each of these terms.
To combat spam, malware, and phishing attempts it is advised that you use have installed and updated on your computer the following:
I also advise that you read and follow the advice in this tutorial: Simple and easy ways to keep your computer safe and secure on the Internet
How to enable the Phishing Filter in Internet Explorer 7:
How to enable the Phishing Filter in Mozilla Firefox:
There are many different types of software, protocols, and services available to access and send e-mail. In this section we will explain various technical terms that you may see when using e-mail services.
Q: Is it true that people can read my e-mails while they travel through Internet on the way to the person I am sending them to?
A: The technical answer is Yes. Any time a message passes through a server, that server can examine the message, copy the message, or even delete the message depending on certain criteria. The reality, though, is that the majority of ISPs and companies do not do this simply because it would become overwhelming to store copies of all the mail that passes through their server. At the same time, it is always better to be safe then sorry. So never send personally identifiable information such as social security numbers, credit card and banking information, passwords, etc via e-mail.
Q: Who or what is this Mailer-Daemon or Postmaster that sometimes sends me an e-mail.
A: These mailer-daemon or postmaster emails are automatically generated by the mail server software when an e-mail you sent failed to reach it's intended recipient for some reason. Whether it be you sent an e-mail to a person that does not exist, the recipient's mailbox is full, or the server is having an error, when you receive one of these e-mails it means that your e-mail failed to be delivered. If you open the email they will typically, if you can decode the information, give a reason as to why the delivery failed.
Q: Why does it take so long for someone to receive an e-mail I sent them?
A: When you send an e-mail to someone it should get to them within minutes if not seconds. There are many factors, though, that could cause delays in delivery. Below we explain a few of these factors:
Q: I keep getting messages from someone called Mailer-Daemon saying that I am sending e-mail to people that I never sent to!?!?!
A: I see this question all of the time. You check for new e-mail on your computer and a stream of e-mails from someone called Mailer-Daemon appear saying that your e-mail message to some unknown address failed. These types of messages are typically due to your own computer or someone else's computer being infected with an e-mail worm. E-mail worms typically propagate by scanning an infected computer's address book and then disguising itself as one of the contacts in this address book. It then sends an e-mail to everyone in the list or other randomly generated recipients. When these e-mails fail to deliver for whatever reason, the errors are returned to you because the worm is sending out that e-mail disguised as yourself.
If it is not your computer that is infected there is, unfortunately, not much you can do to fix these types of problems other than try and examine the Internet header of the mail message to determine the IP address of the computer that is sending the messages. You can then hopefully track the user down using this information to let them know they are infected.
Q: When someone sends me an e-mail they get a message back saying it was undeliverable because I have no space left in my mailbox!
A: When someone sends you an e-mail your mail server will store the message in a mailbox on the server. ISPs, though, will typically set a maximum allowable size for your mailbox, and if your mailbox reaches this limit, will generate error messages stating that your mailbox is full to whoever sends you an e-mail. To fix this problem download all your mail off the mail server using a POP3 client such as Outlook Express, Outlook, Thunderbird, Eudora, etc. These types of problems typically occur when someone enables the setting in the mail software to leave messages on the server. When this setting is enabled when you download new e-mail a copy is left up on the server and is never deleted.
Q: Where does e-mail get stored on my computer?
A: When your mail client downloads new mail it stores them in mailboxes on your local computer. Depending on the software you use for mail, the mailboxes will be stored in various locations. Below is a list of the default locations for the more popular mail software packages.
Q: So which is it...is it e-mail or email?
A: Either :)
Now that you have read this tutorial I hope that you have a learned a little bit about the blessing, or the menace, of e-mail. With e-mail being such a large part of our every day life whether it be in work and or play, having a basic knowledge of the under workings always helps. As always, if you have any questions about this tutorial or e-mail in general, please do not hesitate to ask us in our forums.
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