This article was published by PC World in 2008, but the original article is no longer available online.

We've chosen to re-publish the original article here as it provides perspective and is, in our opinion, a somewhat amusing read.

Much like a time capsule back to the early days of email marketing, if you're in the game, you may enjoy this quick read.

The article describes the now ubiquitous technique for tracking email opens: pixel tagging – but makes it sound like crazy spy technology.

It's fascinating to see the authors refer to this as "tracer software" that makes use of a "Web bug".

Also fascinating: the website of the vendor referenced in the article is still online as of this writing, and it's a time capsule in its own right.