The TNEF File Viewer Handbook

Michael Goffioul

Revision 5.3.40 (Applications 16.08) (2016-07-27)

The TNEF File Viewer is an application for TNEF mail attachments.


The TNEF File Viewer allows 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.

TNEF Main Window

This utility program allows to perform various operations on those attachments:

  • View/open attachments with associated applications.

  • Extract actual attachments

  • View message properties (TNEF/MAPI)

  • View/extract message formatted text (in RTF format)

KMail automatically shows the content of a TNEF attachment. You can open or save the attachments using the actions in the context menu.

TNEF attachment in KMail