I can confirm I have the same “header”, one more line about unsubscribe from a newsletter. But that does make sense, could be interpreted as a “newsletter” of some kind. But the message itself is not shown, only a blank window.
The mail is an automated message from a german parcel transport packing station. So you go there, insert your package an click “Send me a deposit receipt.”
I do not know what infrastructure that company is using and if they issue changes on that mail.
I know the use S-MIME/PGP and have documented it at http://keyserver.deutschepost.de/?language=en.
I can deliver a screenshot or source code of that mail, but only if it is not shown in public (data protection 
).