AIP - loss of classifiacation

 

I have been communicating with some of my users, and have been alerted to a possible issue/bug when using AIP.  A user creates and classifies a document.  The user then emails the document to another user.  The receiver then responds to the email.  I am attempting to find out if the receiver opened the document, modified the document, or did nothing with the document. Then the receiver responds to the sender, keeping the document attached to the email.  The original sender opens the document to see that the classification had been lost from the document.  

 

The AIP client is not installed on the receiver's mobile device.  What happened to the classification?