The Practical Mac

How Spammers Verify Your Email Address

- 2003.04.08 - Tip Jar

Have you ever wondered why you get so much unwanted junk email (a.k.a. "spam")? The answer could surprise you.

The simple act of receiving spam can in turn lead to your receiving more spam.

Sound confusing? It is actually the latest tool of spammers in what has become a multimillion dollar industry - the daily sending of millions of commercial email messages.

You may wonder exactly how merely receiving a piece of spam can lead to receiving more spam. Here's how it works.

The pages you view in a Web browser are generally written in hypertext markup language (HTML). Web pages contain two types of content, text and images.

The text is actually contained in the HTML code for the page, but the images are not. They are separate files and may be loaded from a different location. Your browser loads the text first, then sends a request for the images, which are loaded afterwards.

Most email programs can receive HTML-formatted email messages, and your email application displays HTML-formatted messages in much the same manner as your browser: It displays the text and subsequently sends a request to retrieve the images from a remote location.

Spammers can use HTML mail to easily verify that your email address is valid. This is done by embedding your email address in the HTML links that load the graphics. When your mail application connects to the Internet to load graphics from the spammer's website, the spammer can log your address as "known good."

Lists of known good email addresses are a prized commodity in the world of Internet commerce, which means that you will now begin to receive even more unsolicited email.

Here is an example of how your email address may be embedded in a link: <http://www.site.com/yourname@email.com/image.gif>.

In this example, the spammer is attempting to verify the address "yourname@email.com." This is just one common example, and many other variations are possible.

There are a couple of ways to avoid this. First, you can disable HTML rendering in your email program. Almost all email applications, including Entourage and Mail, have a way to do this. Or you can leave HTML rendering on but not use the preview pane in your email application - and never click on a link that says, "unsubscribe." More often than not, spammers use this as a way to verify "good" email addresses.

When you highlight a message in your inbox, the first part of the message displays in the window below it. This window is referred to as the preview pane. Most email programs have the preview pane enabled by default, but it can be disabled. When you see that the message is spam, you can delete it without looking at it or having it display automatically.

As long as you do not open the message or view it in the preview pane, the spammer will think your email address is "bad." This does not necessarily mean your address will be removed from spam lists; it just means you are less likely to be added to any new ones. LEM

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Steve Watkins is the Vice President for Information Technology for a mid-sized bank, an attorney, and an Army Reserve JAG on extended active duty. He has been a Mac user for about 12 years. He has owned some PCs along the way - but always came back to the Mac. If you find his articles helpful, please consider making a donation to his tip jar.

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