Tracking sent e-mail provides a (paid) service for curious people who want to track the emails they’ve sent. It gives you the following information:
– Did they read it yet? / When and how many times did they read it?
– How long did they read it?
– On which computers did they read it? (ip adress, “location”, browser, os, ..)
And the average joe receiving such an email won’t even notice that you’re tracking him.

Enough advertisement, let’s see how this really works so we can do this ourselves for free :-). The emails you send using this service contain a link to a tiny transparant image (1×1 pixels) , if you look at the source of such a tracked mail message you notice this link:

<img src=”; nosend=”1″ name=”dtri” width=”1″ height=”1″>

This redirects to the following script:

What it outputs looks, feels and smells like an (invisible) jpg file but actually is a script which logs all information of the visitor (reader of the email) , and keeps the email client connection alive by sending jpg compatible data at slow speed. It does that to determine how long you’re reading it.
So this only works if images are enabled in the email client of the receiver. I think Thunderbird disables this for people not in your contact list.



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