All you need to know about tracking Open Rates

Open rate is one of the most important metrics in email marketing, we won’t deny that.

In fact, many marketers obsess a little about it. It’s understandable.

Why we consider open rates important

The open rate is the indication of the first action taken towards you email campaign. If subscribers don’t open your email, they can’t see the campaign, and marketing dies right there.

Engagement does not exist without having that open first.

But there is a problem…

The open rate is not entirely a reliable metric. Not only that, but with the variety of environments and how an email is received, the future of this metric doesn’t exactly look too bright.

What I mean is that different email clients work in different ways, Gmail and Outlook for example, work completely different.

How is open rate measured

You would think that open rates depend on an email being opened, but the reality is that it’s measured based on the render of an image.

When an email is open and an image is rendered, the email client points at the server hosting that image and an open is counted.

You see where I’m going with this already, right?

  • A plain-text email is not counted
  • An email delivered to a subscriber that has images turned off is not counted

ESPs add a tiny pixel called “open tracked pixel” in your campaigns in order to measure that open, but this doesn’t solve the issue either, if images are turned off.

On the other hand, you have email clients like Outlook that count the open even if the email was just skimmed in the preview pane, but it was never opened.

Like I said, the problem with measuring email is that we depend on several different environments that behave in different ways.


Gmail made 2 significant changes in 2013 and 2014:

Image caching

Image caching means that Gmail stores the images in your email in their own servers, including the open tracker pixel. If the email is reopened, Gmail serves the cached image from its own server.

What’s the impact? It simply means that opens are only counted the first time, additional opens are not tracked.

Also, image caching eliminates the possibility to determine where exactly was the email opened, if it was on the browser or on a mobile app.

Automatic images

If you haven’t noticed, Gmail no longer asks you if you want to display images or not, they are automatically downloaded. This has raised some concerns about privacy, but that is not out focus here.

What’s the impact? A more reliable open rate. In fact, this change might have cause an increase in opens in your campaigns. Litmus tracked the impact (see the image below).

Gmail open rates

Why is open rate still important then?

Even with all those issues, open rate is still important to track. The open rate can be used an as indicator of possible changes in your email marketing.

Just as Litmus identified the increase in opens due to the Gmail change, you could also find a sudden decrease. It’s time to do some investigative work in different areas of your email marketing.

For example, a decreasing open rate should be something to pay attention and use it as a staring point to explore possible issues in your list.

It could mean that you are suddenly having deliverability problems, it could also be an indication that your segmentation is not working.

The future of email metrics

Email is more than 40 years-old, and for many decades it didn’t suffered any major changes, but it has been trying to catch up with technology in the last few years.

There are some services, like Litmus and Return Path, that already offer much more valuable and reliable metrics than simply knowing how many people open your email, like…

  • Knowing if they glanced, skimmed or read your email
  • What device and email client they opened with
  • Did they forward of printed the email
  • Geolocation data of the open
  • And individual level tracking

While this is currently happening outside your ESP, we’ll hope that they either integrate or catch up with technology. As I mentioned before, these services are paid.

For now, let’s keep tracking opens with the tools we have, and use it not only to see how many people opened, but also as an indicator of changes in your list.

No homework, but I hope you now have a better understanding of the state of the open rate. 😉