What do unique opens measure in email marketing?

Unique opens in email marketing specifically measure the total number of delivered emails that were opened by separate recipients. This metric is crucial because it reflects the engagement level of users with the email content. By focusing on unique opens, marketers can ascertain how many distinct individuals found the email appealing enough to open, regardless of how many times they may have opened it. This helps in understanding the effectiveness of subject lines, the timing of the email sends, and the relevancy of the content to the audience.

In contrast, the other options focus on different metrics that do not accurately represent what unique opens entail. For example, tracking clicks involves a different aspect of engagement, while revenue reflects the financial outcome of a campaign and unsubscribes measure disengagement. Each of these has its own significance, but they do not define or contribute to the unique open rate.