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Understand open tracking and link tracking
Understand open tracking and link tracking

Gain extra insight into what your contacts are interested in.

Gareth Burroughes avatar
Written by Gareth Burroughes
Updated over a week ago

How open tracking works

We can track opens in HTML emails using a hidden pixel automatically placed at the bottom of your emails. Once the images are downloaded in the email, we register the email as open. We also register an open when a contact clicks a link without downloading the images.

However, there is a difference between HTML and plain text link tracking. The recipient must click a link within the email for us to register it as open for plain text emails. This is because plain text emails don't contain the hidden pixel we use in HTML emails.

For link clicks, we record:

  • Date clicked

  • URL

  • IP address

  • User-agent

Learn how to access the user-agent web browser information in Using the Unique clickers report.

Link tracking

All tracked links are redirected through your sending domain. We add a URL string to the end of each link, for example, this might look like this:


Links are appended with either dm_i or dm_t.

  • dm_i is used for live sends

  • dm_t is used for test sends

Problems with Google Analytics 4

We're aware that this way of tracking links can be problematic, especially for Google Analytics 4 tracking.

Sometimes we have to add links to the tracking excluder because the addition of dm_i or dm_t causes the site to redirect to the wrong page. As a result, some sites don't accept the addition of our query strings (or anyone else's for that matter) on their site, which then causes a 404 error or linking to the wrong page.

Although this feature can't be disabled, there are two workarounds:

  • You can set up a rule in Google Analytics 4 to ignore dm_i and dm_t from your links.

  • We can add certain domains to our tracking excluder where we wouldn't append dm_i or dm_t to any links associated with your domain. The link won't be trackable through ROI or Web Behaviour Tracking but can be tracked in Google Analytics 4 and email reporting.

If you need to, you can edit a link post send, but you can't change it to a 'not tracked link'. However, you may be able to edit the link to remove the UTM tags.

When a contact is deleted from an account

In this case, we hide the email address in the reporting and replace it with a 'Deleted contact' value, so that the statistics of your email reports aren't affected. All other data held against the contact is removed, and therefore not displayed, but the following will still be accessible in-app:

  • Date clicked

  • URL

  • IP address

  • User-agent

Tracking exclusion

Even if you remove UTM tags, Dotdigital's tracking script will still be at the end of the URL, which should look like this: ?dm_i=0,0,0,0,0. This is used by a couple of add-ons in Dotdigital, being ROI and Web Behaviour Tracking. If you're using neither feature, we can add the domain to what we call our tracking excluder; this will remove the addition of ?dm_i=0,0,0,0,0 at the end of the URL. The link would still be trackable through email reporting, but not trackable through ROI or Web Behavior Tracking.

If you want to reverse this, we can delete the domain from our tracking excluder; just get in touch with the Support Team if you do need the domain removed.


The tracking excluder only removes the addition of our ROI and Web Behavior Tracking script from your campaign's URLs. Keep in mind that some sites don't like additional query strings applied to the end of links that redirect to their sites, for example, ?dm_i=1AAA,2BBB,CC3CC,DD4D,5. Adding the tracking excluder helps in these situations, but it's not a solution for all sites.

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