The Process Behind Open Tracking in Email

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 the email is logged as an email open event. Typically the image is transparent so a recipient can't see it, and typically it's tiny - 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 in 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, in that adding the pixel to the email is relatively easy. However, once that email is sent, the complications begin. Common scenarios can cause the unfortunate false positive or false negative result.

False positives: Sometimes emails are marked as opened 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 most recent email. This can cause the tracking pixel to be downloaded, however, the recipient hasn't actually 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 any 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?

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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.

Note: Our tracking pixel is hosted on Heroku, so that pixel shows as a Heroku URL.

If you're sending emails though our Chrome extension you can disable open tracking for those messages if you so choose, from your Apollo Settings:

You can also read more about the Chrome Extension here!

How Should I Approach Email Opens?

The key word here is relative, as it's important to track how your open rates are evolving over time. However, as you continue to send your blasts out, 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.

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.

Why Are My Own Opens Being Tracked?

Check out this resource for more information on what causes this, and how to avoid it.

Where Does Apollo Detect Email Opens?

Email opens can be detected on separate open instances such as the user's operating system, browser or email client, for example:

Operating System: Mac
Browser: Microsoft Edge, Windows
Email Client: Gmail

Here's an example of an email open detected on a browser:

• Important Note: We will show the user's open location if it's detected on the operating system and not on an application (browser or email client).