Last night I got an email that surprised me:

As you can see it is showing an updating countdown counting down to a specified date.

I started wondering how this was possible so I looked at the code and my first guess was validated:

  <img src="" alt="Countdown" border="0" style="display: block">

They are referencing a php script which returns an animated gif. You can actually copy the url and play around with the time parameter to see how this changes the image.

Now the only question was: How long are they looping and how costly is the size wise: The answer: For each request a new image with a length of one minute is generated. I guess they assumed that no one will look at the email for more then a minute or if they do will not notice the jump back. You can see that jump here:

This comes at a size of, 176K, it’s still a gif but not as bad as I had imagined.

I thought this was quite a cool hack, it certainly was surprising and caught my attention to see anything update in my mail client.

But on further inspection it turns out that this seems to be quite common in email marketing and there are even services for this or for dynamic emails in general.