Unfortunately, tracking e-mail open data is accomplished using an image technique that is not 100% reliable. We can tell when an e-mail is opened because of a tiny invisible image that is included in the e-mail; when the image is loaded, Bill4Time is notified.
However, if your customer’s e-mail provider does not load images automatically (which some do not), Bill4Time will not be able to tell if the Invoice has been opened or not.
In other words, an “Opened” label guarantees that the e-mail was in fact opened, but the absence of an “Opened” label does not necessarily mean the e-mail was not opened.
Our developers are looking into ways to improve that if possible, but we are currently unable to force those providers to allow for our tracking to go through.