This email metric estimates the number of clicks against the total number of emails delivered or the number of emails sent. It is a percentage metric with various definitions across different reporting and sending platforms.
The easiest way to assess your email’s engagement is the click-through rate. It is the opposite of click-to-open rate because it shows activity out of everyone that gets an email in their inbox. With this, email marketers can see the proportion of their audience that is interested in their messages over time.
It is common to see Email Service Providers using unique clicks to measure the click-through rate. However, this is not universal. A unique click is always recorded the first time a subscriber clicks on a campaign. Subsequent clicks, no matter how many, are not tracked or recorded as unique clicks. So, the primary role of measuring the click-through rate is to assess engagement.