HOW DOES E-MAIL WORK?

You send and receive it everyday, it’s instantaneous, and it doesn’t cost a thing. It’s E-MAIL, one of the most important tools of today. Let’s take a look at how it works, under-the-hood and in normal language.

What Is Email?

Electronic mail (abbreviated as e-mail, email, E-Mail, etc.) is a very old form of computer-based communication.
A long time ago – in technological, not human, terms – computers were giant machines. People used dial-up terminals to access them, and each machine held storage for multiple users. As is the case with any community, people found useful and unique ways to communicate with one another, and a messaging system evolved. The caveat was that you could only send messages to other users on the same system, at least up until 1971. As the story goes, along came Ray Tomlinson who sent the first email by addressing a user on another system using the ‘@’ symbol. Obviously, both the underlying dynamics and far-reaching consequences weren’t so simple, but it was that notion that brings us to where we are today.

Email was, at that time, the equivalent of today’s text message. Over time, it changed and evolved like anything else; it has sender and receiver, a subject line, a message body, and attachments, but on the whole, emails are pretty simple documents. It’s not so easy to get it from point A to point B, however. Like anything else, there’s an intricate process involved that works behind the scenes to make it seem as seamless as possible. A lot of the ideas used in relaying email were important in formulating document transfer, which is at the core of things like bulletin board systems and the world wide web.

WHAT'S NEXT?

When someone, let’s say a seller, sends an email, it has to have an address in the form of "user@domain.ext". Our example has seller@gmail.com. The email gets sent by the client to an outgoing mail server via Simple Mail Transfer Protocol(SMTP). The SMTP server is like your local post office, which checks your postage and address and figures out where to send your mail. It doesn’t understand domains, though. They’re a sort of abstract thing, so the SMTP server contacts a Domain Name System(DNS) server. The DNS server is a sort of phone or address book for the internet; it translates domains like “gmail.com” to an IP address like “ 254.254.254.254.” Then, it finds out if that domain has any “MX” or mail exchange servers on it and makes a note of it. This is like your post office consulting maps of where your mail is supposed to go, calling their local post office, and checking to see if your friend has a mailbox or P.O. box to receive mail.

Now that the SMTP server has the proper info, the message gets sent from that server to the target domain’s mail exchange server. This server is referred to as an MTA, or Mail Transfer Agent It decides where exactly to put the mail, much like how your friend’s post office figures out how best to get it delivered. Then, your friend goes and fetches the mail, usually using a client that works via "Post Office Protocol" or
" Internet Message Access Protocol".

Unlike your physical mailbox, your outgoing and incoming mail are handled by two different types of servers. There’s really no discrimination towards receiving servers; any computer can be made an MTA pretty easily and handle things well. Sending mail is a different story. SMTP servers must have static IP addresses, and most ISPs block port 25 so that their users can’t send mail themselves. Why? Because of the massive amounts of spam gnawing away at our collective bandwidth, the very stuff your MTA should be configured to filter out. You can configure your clients to use your ISP’s SMTP server in lieu of running your own. The point is that you need both an MTA and an SMTP server to use email, as each is specialized for what it does.

Anatomy of Search Engines

Search engines are the key to finding specific information on the vast expanse of the World Wide Web. Without sophisticated search engines, it would be virtually impossible to locate anything on the Web without knowing a specific URL.
But do you know how search engines work?
And do you know what makes some search engines more effective than others?

When people use the term search engine in relation to the Web, they are usually referring to the actual search forms that searches through databases of HTML documents, initially gathered by a robot.
There are basically three types of search engines:
Those that are powered by robots (called crawlers; ants or spiders) and those that are powered by human submissions; and those that are a hybrid of the two.

Crawler-based search engines are those that use automated software agents (called crawlers) that visit a Web site, read the information on the actual site, read the site's meta tags and also follow the links that the site connects to performing indexing on all linked Web sites as well. The crawler returns all that information back to a central depository, where the data is indexed. The crawler will periodically return to the sites to check for any information that has changed. The frequency with which this happens is determined by the administrators of the search engine.


Human-powered search engines rely on humans to submit information that is subsequently indexed and catalogued. Only information that is submitted is put into the index.

In both cases, when you query a search engine to locate information, you're actually searching through the index that the search engine has created —you are not actually searching the Web. These indices are giant databases of information that is collected and stored and subsequently searched. This explains why sometimes a search on a commercial search engine, such as Yahoo! or Google, will return results that are, in fact, dead links. Since the search results are based on the index, if the index hasn't been updated since a Web page became invalid the search engine treats the page as still an active link even though it no longer is. It will remain that way until the index is updated.
So why will the same search on different search engines produce different results? Part of the answer to that question is because not all indices are going to be exactly the same. It depends on what the spiders find or what the humans submitted.
But more important, not every search engine uses the same algorithm to search through the indices. The algorithm is what the search engines use to determine the relevance of the information in the index to what the user is searching for.

One of the elements that a search engine algorithm scans for is the frequency and location of keywords on a Web page. Those with higher frequency are typically considered more relevant. But search engine technology is becoming sophisticated in its attempt to discourage what is known as keyword stuffing, or spamdexing.

Another common element that algorithms analyze is the way that pages link to other pages in the Web. By analyzing how pages link to each other, an engine can both determine what a page is about (if the keywords of the linked pages are similar to the keywords on the original page) and whether that page is considered "important" and deserving of a boost in ranking. Just as the technology is becoming increasingly sophisticated to ignore keyword stuffing, it is also becoming more savvy to Web masters who build artificial links into their sites in order to build an artificial ranking.