Do people who have email preview panes set up in outlook who can read emails without clicking on them count as 'non-openers?
Thanks for reaching out to the Community! We track opens by placing a 1 pixel image within the campaign. If the preview pane is displaying images, then it will be tracked as an open. If the preview pane does not display images, but the subscriber clicks a link it will also be tracked as an open. You can learn more here.