Winmail Opener: How to read TNEF-encoded email messages

Not long ago, I covered TNEF View, a utility for reading email messages encoded in Transport Neutral Encapsulation Format, the proprietary format Microsoft uses to encapsulate messages. Microsoft Outlook and Exchange

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Server often store and transport messages in TNEF format.

To non-Microsoft mail readers, a TNEF email looks like a plaintext copy of the message with an attachment named WINMAIL.DAT. The attachment contains a richly formatted version of the message, any OLE-embedded objects, any Outlook-specific features (such as custom forms), and attached files or messages.

An email client that doesn't know how to interpret TNEF will simply display such a message as a plaintext email with WINMAIL.DAT listed as an attachment -- which means that any attached data will be unreadable.

One way to get around this issue is to use an external program that reads TNEF. I've recently encountered a free application called Winmail Opener that handles the vast majority of the work needed to decode and understand TNEF.

Winmail Opener runs a few different ways:

  • As a window into which you can drag-and-drop TNEF-encoded files
  • As a command line, which you can use to do batch decodes of many files
  • As a right-click context menu item, which can be used to open TNEF files from Explorer or associated with .DAT files

When you first launch the program, it gives you a wizard-style interface for opening messages. When a message is dragged and dropped onto the program, its text and any assorted attachments are listed and can be extracted and saved.

When run as a command line, it takes up to two parameters -- a source file and a target directory -- and can be used in conjunction with a batch file to automatically process all messages in a given directory.

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter.

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Related information from SearchExchange.com:

  • Tip: Decipher a WINMAIL.DAT package without using Microsoft Outlook
  • Our SearchExchange.com experts' favorite freeware
  • The Microsoft Outlook Toolbox
  • Reference Center: Outlook and Exchange administration tools

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    This was first published in July 2006

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