DidTheyReadIt.com – How it works
This Web site allows you to track whether your email is read by the person you sent it to. To use it, you first sign up the site, then send emails to email@example.com. Your email travels via their server on its way to your recipient. You then get an email back from DidTheyReadIt telling you when the recipient opened it and some other details about the internet connection they used to open it (including a guess at their city).
In this case, email tracking is accomplished by inserting a tiny image into your email. When the destination email program (or Web browser) opens the email, this image is requested from the DidTheyReadIt.com web site. The HTML image URL has special parameters to match it to your original email. This is similar to how page counters work on normal Web pages.
You can tell if you have been sent an email from someone using DidTheyReadIT by looking at the email message headers. This is usually available under the options for your email client. Try checking the properties of the message, or viewing the “full source” of the email. Look for something like:
Received: from 220.127.116.11 (HELO dtri1.rampellsoft.com)
This tells you the message traveled through RampellSoft – the makers of DidTheyReadIt.
You’ll also see the image tag for the invisible image:
<img src=”http://didtheyreadit.com/index.php/worker?code=d410bef96e7ca16da181fccd1f17a181″ width=”1″ height=”1″ />
Another interesting thing is that they claim to report how long your email was viewed. I’m not sure how this works – but perhaps they keep the connection open between the viewer’s Web browser and their server while sending the image. I haven’t seen the length be greater than 2 minutes 15 seconds.
This technique won’t work if the person you send the email can’t view HTML emails. Also, many email applications (like Hotmail) allow you to turn off images in HTML emails. This is useful because Spam can contain “image bugs” like the one used here. When you open the email, the spammer knows he has a good email address and can follow up with lots more spam.
It would be interesting to use this for one of those false and misleading emails that get sent around saying “Bill Gates is tracking this and will give everyone who opens it $25.” Forwarding a DidTheyReadIt.com email could almost make this sort of tracking feasible, but in my experiments forwarding HTML emails, the content and images are quickly lost or reformatted.