A researcher at the University of Cambridge has found a novel twist on spam that turns out to be a completely different kind of attack. The email is a convincing forgery of a DHL email. When opened, the PDF comes up as a blurred screen with a message telling the user that the document is secured and he must visit a special link in order to see the complete file. The message also includes a line at the bottom encouraging the recipient to move the message to his inbox if it happens to end up in a spam folder.
Source: https://threatpost.com/phishers-going-the-long-way-round-to-avoid-filtering-systems/113170/