Email Open Tracking & How It Works

By DB Hurley · PUBLISHED June 06, 2018 · UPDATED June 06, 2018

This quick post is the beginning of a short series entitled Marketing Basics. This new series will share some basic marketing automation 101 information. In this short post we'll explore the concept of read-receipts as they were historically defined and then the more modern email-tracking as done by Mautic and other marketing automation software. Throughout this series we'll cover a variety of topics as it relates to marketing and marketing automation from a beginner's standpoint. 

The most common way to ensure that your email was delivered (and subsequently read) is through the use of “read receipts”. Most desktop mail clients these day allow for this functionality by employing an email tracking option. Prior to sending your message you can elect to be notified when a recipient has either received or read your message.

The problem with old-school read receipts

This plan isn’t foolproof though for multiple reasons. The greatest problem with email tracking through read receipts is the potential for requiring the recipient to actually send the read receipt. Rather than a passive, behind-the-scenes automatic notification some email clients display a visible notification to the recipient that the sender has requested a read receipt and forces them to take some action (either send the read receipt or not). In these situations the recipient may feel the read receipt is invasive or just plain inconvenient.

By default these read receipts typically send the open/delivered response back to the email inbox of the sender, which if you have configured replies to be ignored or re-routed, this would be unsuccessful (e.g. no-reply@...).

Based on these somewhat problematic shortcomings of the older “read receipt” technologies many modern businesses have moved to using either marketing automation software or even basic email tracking services to provide this same functionality in a different way.

The modern equivalent of read receipts (tracking)

In the case of these alternative services most function on the basis of a tracking pixel (a simple 1x1 image) placed in the email which resides on the sender’s server (or in the sender’s marketing automation platform). If an email is opened the sender’s computer or device will also attempt to load the tracking pixel as it parses the HTML from the email.

When the the 1x1 graphic is loaded from the sender’s server it also notifies the sender (or the marketing automation software) that the image has been loaded by the recipient’s device. As you can begin to deduce that tracking pixel has additional information attached to it that is passed to the service along with the request for the image. The following is an example of this (beware, some HTML to follow):

<img src="“[email protected]”" />

As you can see from the above example which I admit has been drastically reduced for ease of understanding and certainly is not a live example, the source for the image is location on the sender’s server. Their subdomain on their marketing automation software platform followed by the specific 1x1 transparent gif file which will be returned. But the trick is in the final part of the source. The last bit after the “?” provides additional information to the sender - in our rudimentary example above it also sends the recipient’s email address back along with the request for the pixel.

Tech side note: The 1x1 transparent tracking pixel is usually not an actual file living on the sender’s server, but a functional endpoint that parses through all the extra information sent to it in the “request” and then creates a 1x1 transparent image file to return at the end of it’s functional process.

This is information which the sender’s software will be able to parse out and track. As such each tracking pixel is unique to each recipient and the sender’s software is able to determine every time a particular recipient opens an email. This is the same way in which a sender can be notified each time a recipient re-opens an email as well…the above example is simply repeated and the transparent 1x1 image reloaded (for the more advanced reader, I am aware that caching might mitigate this re-open in some cases and there are advanced techniques to by-pass that caching but those methods extend beyond the scope of this answer)

Getting more advanced results and additional information

By implementing this manner of read-receipt or email-tracking you are able to successfully “monitor” and observe who is opening your emails. Often these same software packages will also handle the more basic soft and hard “bounces” as well which are used to determine whether the email was truly delivered in the first place to the recipient’s inbox. In an effort to remain concise that explanation will be saved for a different answer.

It used to be that marketing automation software was ridiculously expensive and insanely difficult to setup and run. Thankfully the technology has improved drastically and the market has opened up tremendously and with our amazing community and the outstanding Mautic, open source marketing automation platform everyone now has access to this technology!

I hope this post has helped you better understand email tracking, deliverability, and email opens. In the next in this intro tutorial series we'll focus on click tracking, the tech behind how it's done and why it's important.


Carlo Bruno


What about the clients that stop downloading the images unless the user actually click to authorize them? It looks similar to send a "read receipts" :-( Carlo
DB Hurley

In reply to by carlojbruno


You're absolutely correct, however with this approach there is a much higher % of individuals who will simply have this set to auto-accept/auto-authorize. There are of course still similarities.

If I send a mail with tracking on, and then I open the same mail from “sent item”, it will read the image and will appear as mail has been read since the image was loaded again. And as such even though the receipent hasn’t opened the mail, system will still show it as a read mail. How can we handle this?
Swarnendu Dutta

In reply to by Gtk


I guess the part where "[email protected]" will track the email address who has opened. You can check the contacts and see the list there.

In reply to by Gtk


We have to set more tracking params to the url along with recipient email based on our business requirements, For this case may be we can set the IP range as one param, and while tracking receipts we can check if the opener is not from this ip range, then only only track this is real opening.
Ike King

Great post, these tips will help with my marketing efforts. thanks for sharing.