In order to track when an e-mail has been opened, a pixel is placed in it. There are e-mail servers that don’t accept these kind of objects (pixels). Is it for this reason that it doesn’t allow us to track if the e-mail has been opened or not.
That way, if the e-mail appears as not opened, it might be because the tracking just works when the recipient doesn’t have this kind of complement blocked. In this case this depends on the e-mail provider and not on Signaturit.
As a solution to this problem, if you need to validate that the content of an e-mail has been read, we recommend you to send it with an attached document and select "certify open document" This action is validated by Signaturit since the whole process is done through us.