> It has since been opened by 26% of my subscribers, that's 4,600 people
Sadly, open rates are no longer a useful metric in the absolute, at all. Some email providers will block all tracking pixels (so those people look like they never open anything, unless they click the link) and others will proxy all images, so they fire all tracking pixels systematically (so these people look to you as if they open every single email).
The only use you can make of open rates today is relative: "was the open rate higher or lower this month than last month?"
But it's extremely unlikely that your actual open rate (and list of who actually opened) is anywhere close to what the stats show. The only thing that still makes sense is click rates.