Why is the tracking code showing as a broken image in my email?

As you may already be aware, the tracking code we provide for you to place in each email campaign is actually a tiny, 1px image.

In the majority of email clients this 1px image stays hidden and is never noticed however in some webmail clients, such as Outlook 365, it can be visible and appear as a broken image. This is caused by the way the web browser handles the image and is not something Litmus can control. 

Unfortunately, we cannot control how the web browser renders the image without affecting the functionality of the tracking code. Our development team will continue to investigate this issue, but our main concern is that it doesn't compromise our system's tracking functionality.