4 min read

How Email Open Tracking Works

By Mike Donnelly on Mar 20, 2017 6:15:35 PM

How Email Open Tracking Works

Have you ever wondered if your emails are being read? What time your recipients opened them, where they were and what devices they used when they opened them? 

Marketing automation systems like Marketo, Constant Contact, Mail Chimp, Eloqua, Act-On, Hubspot, etc. all use email open tracking as a way to measure the success of email campaigns. 

In this post, we'll review how these technologies work and explore potential pitfalls of over reliance on open rates as a marketing metric.

What is email tracking?

Email tracking is a method of monitoring data from sent emails to the intended recipient to make better informed business decisions. Most tracking systems keep track of opens, times and dates, locations and IP addresses, and even what device the email was opened on. It also keeps track whether links and attachements in the email was clicked on.

Why track emails?

Email open tracking pixels are widely used by marketers an salespeople, and likely almost all marketing emails that land in your inbox are being tracked to some degree.Tracking open data can be helpful for a number of reasons including:

Improve email marketing content - By using email tracking, you will learn what types of subject lines catches the most attention and what content fuels the most engagement. These data will tell you what your subscribers want to recieve more from you and what area you should focus on, and how you can better segment your list that go beyond buyer personas and demographics. Over time, you’ll make better and hyper-relevant emails that will resonate with your readers.

Sales and marketing alignment - If marketing and sales team are properly aligned, transfer of information and data is streamlined. This is vital to businesses because data drives businesses to success. If marketers know which kind of content subscribers are focusing on and are properly conveying them to the sales team, they can better understand the needs and pain points and adjust their messaging to the customer.

Build better relationships - At the end of the day, marketers keep track of emails because they want to build better relationship with their readership. Knowing what they like best, the values they hold dear, how often they like to hear from you, and what time they want to read your emails are all efforts to understand them better. If trust is established between you and your readers, you gain their loyalty and are more likely to engage with your brand more.

How does email open tracking work?

Here’s how email open tracking works:

Step 1: A marketers or salesperson composes and sends and email from a service that uses tracking pixels.

Step 2: A 1x1 transparent pixel, think of this as a small picture you can’t see, is inserted in your email or on a specified hyperlink within the email.

Step 3: Recipient opens your email. The 1x1 transparent pixel picture is downloaded from a remote server, a notification is then sent to the marketer that the emails has been opened.

Potential issues with email open tracking

Take note, based on your recipient's email service provider (ESP), interface, and settings, your reported “open rate” may not be accurate for a number of reasons.

Images can be blocked by default- An example is Microsoft Outlook. By default, images aren't downloaded due to security concerns . It's up to Outlook users to click the “download pictures” button in order to receive a notification that the email was read.

Pixels may be pre-downloaded automatically - Apple’s latest iOS 15 update which was released on September 2021 allows Apple Mail app users the option to choose to hide if and when they open marketing emails. With Mail Privacy Protection turned on, location tracking and open rates are severely affected as all emails received will appear as opened by the subscriber.

Users can install blockers - Even if your subscribers are not using a platform the blocks pixels or downloads them by default, they could use a 3rd party tool or extension like PixelBlock or Ugly Email that prevents their emails from being tracked.


Even with the potential for inaccuracy from email tracking pixels, email open rate is still an extremely powerful metric for marketers to track. While we can’t know for sure if our open rates are being inflated, or artificially suppressed, but we can see trends of increases or decreases and also see changes from email to email. These observations can guide us and allow us to test hypothesis around what kind of subjects lines, content, or send times work best for our audience.

P.S - If you’re a HubSpot user who wants to split test emails or workflows, we’ve got a free tool you might want to check out. Click here to learn more.

Mike Donnelly

Written by Mike Donnelly

Founder and CEO - Seventh Sense