BenchmarkONE uses a tracking pixel to track whether or not a contact has opened an email. The tracking pixel is a 1 pixel by 1 pixel image which is hidden from view. This is a common practice and widely used to track email opens.
The primary reason that you would see no "opens" in your dashboard view is because of the user's mail program blocking images. Outlook and Gmail sometimes do this by default.
Some possible scenarios:
If a contact opens your email but does not show images, we will not track the email open.
If a contact opens your email and does show images, we will track the email open.
If a contact opens your email and does not show images, but clicks on a link within the email, we will track the email open.
Learn more about Tracking Email Opens.