This happens from time to time, unfortunately, and is usually caused by the recipient's email account not being configured to download/display images (our tracking pixel takes the form of a 0x0 .png image file).
Our product team and developers are looking at ways to prevent Mailtrack from flagging opened emails as being unopened, however, due to the technical complexity involved it might take a while for a solution to be implemented.
Our product team and developers are looking at ways to prevent Mailtrack from flagging opened emails as being unopened, however, due to the technical complexity involved it might take a while for a solution to be implemented.