Have you ever gotten one of those emails that promises to give you a prize, or otherwise reward you based on how many people you forward an email to? Well, contrary to popular belief, it is actually possible to track how many people get forwarded to, from any email you send out to anyone. In this article I will explain the very simple methods needed to accomplish this.

A prerequisite for this trick, is to have a web hosting account on a web server, or have your own web server set up, and you will need access to the access log files from that web server.

Now you need to create an HTML image tag that calls any URL on that web server from the body of any email you want to track. The image file it calls need not exist on the server, as you will still get the attempted access logged with a 404 error if you use an invalid URL on your web server.

Below is a sample image tag, complete with a fictitious URL, that identifies the person you first sent this email to be forwarded to.

<img src="http://www.rayslinks.com/tracking/username-mail.com"
 style="visibility: hidden;"/>

Note that to make it simpler to code, I have used a dash character in place of the @ symbol that would normally be in the email address that identifies the person I'm sending the email to, which is appended like a file name to the end of the server's domain, and path in the image tag.

I use Thunderbird for email, and I have the Stationery add on which allows me to edit the HTML source of messages, so I can easily add the image tag to an outgoing email.

Once the person on the other end receives the email, and opens it in their email client, as long as their email client attempts to load the hidden image, it will send a request with headers to my server for an invalid URL with their email address as a file name, which will show up in my server logs as a 404 error, along with the headers they sent.

With those headers will arrive the ip address of any computer that loads, and views that email as it gets forwarded around the web. You can easily count how many people a friend or colleague forwards your emails to with this trick.

Those email headers should also tell you what email client they are using in a User-Agent header, and various other bits of information about each person's computer that reads that forwarded email.

Now it becomes a simple matter of searching your server log files for the word "tracking" to find the image load attempt references, to count how many people got forwarded to.

A much simpler use of this trick is to use it to verify that an email address you send the email to is valid, as it will only generate a server log hit if that email exists, and reads your email.

Some email clients like Thunderbird do not load images by default when you select a message to view, but only loads it's images if, and when you decide to click a "Load Images" button.

Not loading the images by default is handy if you don't want spammers using this trick to verify your email address. Simply never click load images in any spam emails sent to you, and you will maintain your privacy.

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