Digital Life Computers 101
Computers 101: What is email? Or why it isn’t for file sharing.
beingzoe about 2 years ago | 1 response    

If you use a computer the odds are you have an email address, even if you don’t have regular access to the internet. People send billions of emails a day, but like most technology, most people have no idea what it is or how it works. But with email being the single most used and abused communication tool in existence it might help you to understand the basics of what email is and what it isn’t.

• Email is a text message copied and transmitted to one or more recipients.
• Email in your inbox is really one big text file with bookmarks (called headers) that indicate where one email ends and the next one begins.
• Email attachments (even your pictures and spreadsheets) are converted to text format and back to pictures or spreadsheets when you receive them.

But to really understand email we need to cover a few basics about how the internet works and how your computer interacts with it.

• The internet is actually a number of network protocols that define the rules for communicating between computers.
• Server software on one computer manages the rules and routing for a given protocol
• Client software on another computer connects to the server software and interacts with it

To put this in more plain english, when you open your web browser (Firefox, Safari, Internet Explorer aka the big blue E on your desktop) you are opening a client.

When you type an address into the address bar or open a bookmark you are telling your client (the web browser) to interact with the server (the web server that has the published information you want to see). The client asks for it, the server finds it, and sends it back to be viewed and your client formats it for you. Pretty simple.

Protocols and why you don’t know what they are

Many people think of the internet as web pages, but in reality that is only one protocol, HTTP (Hyper Text Transfer Protocol), more commonly referred to as the world wide web. There are many protocols such as FTP (file transfer protocol) to transfer files between computers, and SSH (Secure Shell) for secure access between two computers.

The protocols relevant to our email discussion are SMTP (Simple Mail Transfer Protocol), POP3 (Post Office Protocol), and IMAP (Internet Message Access Protocol).

Servers and Clients

For the protocol to mean anything you need software to use it. To use a protocol you install a client that communicate in that protocol.

But the client is useless unless there are servers to respond to the client requests.

We often refer to the server computer and think of it as a single entity. In fact a server computer is typically just a computer devoted to running MANY server programs. One server computer may be running dozens or hundreds of server programs. Thus the term server can be ambiguous out of context.

The client/server relationship can be thought of as a conversation with a college professor. The client asks questions and the server listens and responds to those questions with information.

You have at least two clients on your computer. A web browser client and an email reading/sending client. You rarely hear anyone call them clients. They are referred to by what they do or a brand name, and the software developers over the years have done a great job of reducing the learning curve for beginning computer users to get started. Thus you have no idea what a client or a protocol is, until you have a problem and when you get on the phone with tech support they probably start asking questions you simply don’t understand.

Email is a text message, one long text message

If you say “text file” to most people they think of opening MSWord and typing something. But that isn’t actually text as far as the computer is concerned. Word processors use some flavor of RICH TEXT which is it’s own special language for determining what “text” is “bold” or “blue” or “24 point size.”

A text file on a computer is literally textual characters in a file with NO formatting other than “new lines” and “empty spaces” that you perceive as paragraphs and spaces between the characters.

And email is just one of those text files. Even when you have attached a picture to it, it is only a text file.

In fact, when you receive email in your client (feeling pretty smart that you know what a client is right about now huh?) the client is reading one text file that contains all your mail in one big text file. Which of course means that when someone sends you an email the server has taken that individual text message (the email) and added it the end of your master email text file (your inbox) to create one big file full of many email messages. Your client does the job of letting you read each message as a distinct email message from a distinct user.

So in reality, even though you have a thousand messages in your inbox, there is only one file that contains them all.

The postman always rings twice and then bounces your email back to you undelivered

Now we understand what client/server software is and that email is really a bunch of text files turned into one text file. But how does it actually get from you to them?

Getting an email address. Telling your mail server who you are.

Well first you have to get an email address. All this means is that we tell the mail server that we want to add a new name to the list of accounts. When we do this the server makes a new text file we refer to as the inbox. Other than adding a password it doesn’t keep track of much else at all, just who should it route and store mail for and the credentials that will be used to access that mail.

Once you have your email address you have to setup your email client. You tell your email client where your mail server is (the server address) and your credentials. Voila you are now sending email.

It really is that simple.

Checking for new mail

When your email client checks for new mail it asks the internet to find the mail server address and passes your request to check mail along when it finds it. The mail server in turn listens to your credentials, checks them against it’s list of users, and if they match it sends back one long text file that is your inbox. Your email client then reads the file into little pieces that you see as individual email messages appearing in your inbox.

Sending mail

Sending mail is the obvious reversal of this process with the extra part of finding the recipient mail server. You create a new text file in your email client. When you click SEND the client asks the internet to find the mail server address, the mail server listens to your credentials, checks them against it’s list of users, and if they match it then asks the internet on your behalf to find the mail server at the address given. If the receiving mail server is found, the sending mail server transmits a copy of your test message and the receiving mail server appends your text message to the big long text file that contains all the email (the inbox).

An email address is actually in two parts, before and after the “". The first part before the "” is the username. The second part after the ”@” is the address of the mail server itself. When a mail server sends a message it doesn’t care about the first part at all. It is looking only for the second part. The receiving mail server only cares about the first part, so that it can see if that username is in it’s list of accounts.

What happens if something goes wrong?

If the any step of the process fails you receive an error message from your mail server or your client. If client can’t connect to your mail server it tells you so. If your mail server can’t find a mail server at the address you supplied it tells you so. If the receiving mail server can’t find the username you supplied in the address it doesn’t tell you, it tells your mail server which tells you. And if your attachment is too big for either mail server your mail server tells you.

Depending on the problem and how the mail servers involved are setup it could take seconds, hours, or days for you to be informed that a message could not be delivered.

If there is no problem your message should be available to the recipient in milliseconds. Yes, milliseconds.

My email takes way longer than milliseconds to deliver/recieve

Yes, I’m sure it does.

That is because while everyone is really sending out a bunch of text messages that should only be a few kilobytes in size, they are really sending high resolution pictures, videos, word processing files, spreadsheets, and really bad jokes.

For reference, a typical typewritten page is 2 kilobytes, an average medium resolution photograph 3,000 kilobytes, and the complete works of Shakespeare 5,000 kilobytes. Note these numbers are “rounded” down for simplicities sake.

So even if you were sending 10 pages of typed text (plain text, not a word processing document) that would be a mere 20 kilobytes and would be transferred in milliseconds from your computer to the receiving mail server. Assuming that the recipient is constantly checking their email, add a second or two for their mail client to wake up, get the new message, and format if for display.

However people are now often sending HTML mail (those fancy formatted emails you get) which is still just a text file with extra information to tell your mail client how to format all that text. That extra formatting information can be as big or bigger than the actual content itself, essentially doubling the size of every email you send and receive.

Attack of the killer attachments

Then when you start adding attachments and we add a whole other step to the process. Encoding and decoding the attachments.

For every attachment in your email your client has to encode that attachment to become text so that the mail servers can send the email at all. Then on the other end the attachment is converted back from text into whatever file format it is supposed to be (a picture or spreadsheet).

So what started out as a simple text message turned into a bloated and highly inefficient way to send files. And sometimes these files are very large thus slowing the whole process down dramatically taking a millisecond process and turning it into a three to ten second (sometimes 10 minute) process.

The server says my email is too big. What is going on?

There are practical limits to what the mail server can handle and still do it’s job. Say you want to email a 5 megabyte file (the complete works of Shakespeare let’s say). No big deal. It’s an awfully big text file but the mail servers and clients churn through it and deliver it in surprisingly swift time depending on the internet connections involved.

Now multiply that by a billion and those mail servers are working overtime, finding accounts, finding mail servers, transferring massive amounts of information and your poor client struggling with all those attachments trying to be as quick as possible because it knows how mad you get when you have to sit there for a minute while it retrieves your email.

The whole process not only slows down your computer and the recipients computer to deal with all that crap everyone is attaching, it slows the entire internet down using the least efficient means possible to transfer files from one computer to another.

Thus to prevent the entire internet from collapsing under it’s own weight, mail servers are set with a limit to how a big of a file may be attached.

My mail server says I can send 100 megabyte attachments, no problem right?

The problem is, what is the limit on the receiving mail server? Your friend or customers mail server might only allow 2 megabyte attachments. So even though you can send it, the email is still going to bounce back. And of course this happens a lot all day long around the world, needlessly slowing down the internet further.

But an even bigger issue is one of simple etiquette. Even if you can send a 100 megabyte file and your recipient has a really fast computer with a high speed connection they have to wait for your 100 megabyte file to download before they can find out whether that other important email arrived.

By sending massive files via email you are slowing everyones life down. Which might not be a bad thing, but it’s kind of rude without checking to see if they want their life slowed down in the first place.

Okay okay, so I shouldn’t send giant files by email. What do I do?

Unfortunately you are screwed. There is no easy way for the average computer user to send big files from one computer to another. Seriously.

It’s not that it is that hard or confusing, it’s just that most people lack the basic understanding of how their computers work behind all those pretty shiny interfaces and even the most basic thing such as using FTP which is designed to send files between computers becomes a major ordeal. And even when you figure out how FTP works, you need a server to send the files to. Everybody could set up an FTP server on their home computers but then you would have to learn about how computer security works to keep from being hacked.

Honestly for years sending files between computers was so ridiculously convoluted for the average user, that it is no wonder that email is the de facto method for file transfer.

And that is why I don’t blame you.

However, in recent years may web services have popped up that make sending large files easy. Simply go to somewhere like transferbigfiles.com or sendspace.com.

Using services such as these gives the recipient the choice of when they download the file. They receive a link to the file instead of the file itself, and the file is then downloaded using http or ftp which is better suited to delivering the data.

In business settings, files are often going to be emailed to a large group of people anyway. So with a little help from the IT department you could also set up easy ways for you to copy files to a central location that you can then send links to instead of the file itself.

And in conclusion…

I don’t really expect people to stop sending file via email. The ability is there and you should use it. I just thought you might like to know how it works, and why it seems so dang slow sometimes. And armed with a little bit of knowledge prevent some headaches.

But now that you do know, instead of whining to the IT department when your massive file gets bounced back, consider using one of the many services created to help folks like you out.

Generally speaking I wouldn’t email an attachment bigger than a few megabytes. But then I can just FTP the file to our many web servers and send you a link myself. For the rest of you who don’t know how to do that or don’t have an FTP server to use, I sympathize and forgive you for slowing the whole internet down. Next time I will be attacking the spammers and giving advice on some email best practices to keep you, your inbox, and your computer safe.

Gotta go email a hundred megabytes of pictures to someone now. Merry day.

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For a much deeper but still friendly explanation of what email is and how email works visit HowStuffWorks.com: How email works

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This is the first in a series of basic computer skills and knowledge articles. I will likely be updating this one and building an entire Computer 101 section here at CoTradeCo to help folks out.

I will definitely be adding more references and external links for more information and study, but I’m out of time for today. Check back soon. And if you have any questions don’t hesitate to comment here and post other questions in the Digital Life and other communities at CoTradeCo.

See more in the series in the post, Computers 101: Welcome to the show. Or why memorizing is not learning. or simply browse the Digital life Computers 101 community blog topic

All Computers 101 articles by zoe somebody are licensed under creative commons, attribution and share alike.

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a day in the life of striatic – oops image used under a
Creative Commons License
courtesy of striatic at Flickr

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You might also be interested in:

• Computers 101: Computer metaphors and conventions. Or why it looks and works like that.