How open tracking works

When Track Opens is enabled for an email – for instance through Email Setup or when sending a Transactional Email – the system will add a tiny, invisible image to the bottom of the HTML content at the time of send. The image reference is unique to each email and recipient.

When the recipient opens the email, the image is downloaded from the system, which then counts it as an open for that recipient, increasing the Total Opens and Unique Opens figures in Email Reporting.

Allowances

There are some allowances that are worth noting:

• As plain text emails cannot contain images, open tracking only directly works for recipients viewing the HTML email.
• Some email clients disable the display of images as standard, unless the recipient consents to allow images to be downloaded. In this case, the tracking image would not be requested from the system, and the open would not be tracked.
• Apple included a new Mail Privacy Protection feature in their Autumn 2021 OS versions. This changes the behaviour so that Apple pre-fetches all email images (via a proxy), causing open tracking always to be recorded for recipients using Apple Mail, regardless of their true engagement.

The system will also log and count an open when a recipient clicks on a tracked link, but only if they have not previously been logged as having opened the email. This requires Track Clicks to be enabled for the email, and in the case of a plain-text email, the link to be explicity marked to be tracked (by surrounding it in parentheses).