This metric is calculated when the email has been opened by a contact.
A unique open means that only one open is counted per customer as subsequent opens are not unique.
The actual number of unique opens may be higher than the figure displayed as not all email marketing providers allow campaign tracking.
View the unique opens on an email campaign
The first way to access the number of unique opens for a campaign is by viewing your individual campaign in the Campaign Summary report.
You can access this by navigating to Reports > Campaign Summary > Click on campaign name > Overview report.
This report shows you the number and percentage of unique opens for your campaign.
The second way to view the number of unique opens is by accessing Reports > Campaign Summary > Send Summary > Who Opened It?
This report shows you the users who opened that specific email campaign.
From this report, you can also view the number of times a user has opened your campaign as well as the time and date the opens occurred.