ktnef 4:4.13.1-0ubuntu0.1 (armhf binary) in ubuntu trusty

 The TNEF File Viewer allows one to handle easily mail attachments using
 the TNEF format. Those attachments are usually found in mails coming from
 Microsoft mail servers and embed the mail properties as well as the actual
 attachments.
 .
 An attachment in TNEF format is most often named winmail.dat or win.dat.
 .
 This package is part of the KDE PIM module.