Kolleno determines whether an email is read or unread using a tiny 1-pixel image (tracking pixel) embedded in the message. When the recipient’s email client loads this image, Kolleno records the email as “read.”
However, this method has limitations:
False Positives (Marked Read When Not Opened)
Some email systems or security filters automatically load images for scanning.
Links or images may be opened by security tools before the recipient views the message.
Forwarding an email to someone else who opens it will also trigger a “read” event.
False Negatives (Marked Unread When Opened)
The recipient’s email client may block images by default.
The email may be read in a preview pane without loading images.
The recipient may read the email offline without triggering the tracker.
Key Takeaway
Read/unread status in Kolleno is an estimate based on image loading, not a guaranteed record of the recipient’s actions.