How Does Email Open Tracking Really Work?

How Does Email Open Tracking Really Work

Email opens are becoming more and more important to sales and marketing professionals, but how do they really work?


Email open tracking started with email marketing. Eventually, the exact same technology made its way into sales software. And now the differences really come down to ease of use of the email sending system.

Email Open Tracking Overview

At a high level, how they work is pretty simple. Any system which informs you when your emails have been opened does so by inserting an image into the email. If that image is downloaded by your recipient, then presto! it is logged as an email open event. Typically the image is transparent so a recipient can’t see it, and typically it’s tiny – about 1 pixel by 1 pixel.


How can the system know which of your recipients opened the email?

Simple – a code is added to each pixel URL. When created, the code is attributed to the recipient and to the email which they were sent. When the image is downloaded, the tracking system can associate the pixel to the email to the recipient and provide an accurate alert.

But the Real World Isn’t that Simple

The outbound part of this whole process is pretty simple. By that, I mean adding the pixel to the email is simple relatively. However, once that email is sent, the complications begin. All too common scenarios can cause the unfortunate false positive or false negative result.

False positives. Sometimes emails are marked as open when they were not actually opened. The following scenarios cause false positives:

  1. The email is displayed in Outlook’s preview pane simply because it is the then most recent email. This can cause the tracking pixel to be downloaded, however, the recipient hasn’t actually ever viewed the email.
  2. The email is sent to a Google or G Suite address, which always proxies every link in an email – e.g. a link to a tracking pixel – and the link is visited as a test by Google, triggering the open event without the recipient ever actually opening the email. Sometimes this happens, though in our experience there isn’t really a rhyme or reason to it.
  3. The email is displayed on a mobile phone’s preview screen by the Google Email app. This sometimes triggers an email open event without the user seeing more than just the subject and first few words – if they even look at the notification at all.
False negatives. Is it possible for a recipient to completely read your email without triggering the tracking pixel download? Yes. Have you ever seen the Display Images header in Gmail or Outlook?
Gmail Display Images Link

If you see this in your own email and there is a tracking pixel in the email, it will not be downloaded. So yes, you can read an entire email without triggering the open event. What’s worse is that the following Outlook versions block images as their default setting: Outlook 2016, Outlook 2013, Outlook 2010, and Outlook 2007.

As a sales or marketing professional, there is a very high chance a good percentage of your recipients are using Outlook, and have not disabled the auto-image-block.

Side note – because so many people use Outlook, any reports about email opens by email marketing or email tracking companies are about as accurate as throwing a dart wearing a blindfold.

How Should You Approach Email Open?

How to approach email opens depends on your role (or if you are a small business, the task you are evaluating).


Email marketing. The key word here is relative. A single open data point isn’t very valuable to you as a marketer. However, as you continue to send your blasts outs, your audience profile is likely not changing a whole lot. So the best thing you can do is compare open rates from one campaign to another.

Email tracking for sales. Relative works here too, as it’s important to track how your open rates are evolving over time. However, a great way to complement open rates is to include a link or a trackable attachment in your email. Links are much more accurate to track if clicked (because they are more difficult to cheat), so using link clicks and relative open rates will give you a more accurate understanding of your engagement.


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