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WinDeveloper TNEF View

WinDeveloper TNEF View - User Guide



Product Licensing

WinDeveloper TNEF View evaluation requires an evaluation license key freely available from Without a license key or once evaluation period is over the software may be used in Freeware mode with reduced functionality. To keep on using the full software functionality follow this link to purchase a license securely.


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Minimum requirements:
NT4, XP, W2k, W2k3
Internet Explorer v4 or higher
MS Outlook 97 or higher Required only if viewing outlook message as *.msg files. For viewing of TNEF (winmail.dat) this is not required.

To install, download the application and run the self-extracting executable. The installation wizard steps should be straightforward to follow. 

As long as you are running NT4 or higher you will be able to view TNEF messages straight away (see below for details on how to open TNEF files). In case you also want to open MAPI messages as *.msg files then MS Outlook 97 or higher must be installed on the same machine.


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Using the application

WinDeveloper TNEF View exposes the internals of TNEF mails from clients such as MS Outlook. The viewer shows the internal encoding of messages and lets you analyze its various properties. The application supports both TNEF encoded mails (winmail.dat) and mails from MAPI stores (*.msg files). 

The viewer interface is organized into two panes. In the left pane message properties are organized in a tree structure reflecting the internal encoding of TNEF messages. Properties vary from simple values such as subject, codepage and message id, to more complex values such as recipient lists, OLE objects, Metadata and attachments.

Different View Modes


The right pane displays the information for the currently selected property. Here properties may be viewable through 3 different view types: details view, hex view and rich view. The active view may be changed from the View menu or through the toolbar. 

The rich view supports the display of OLE objects, metadata and date/time properties. 

The rich view enables the display and activation (running) of OLE objects. The previous figure showed the display of one such object. Activating an OLE object just involves double-clicking on the right pane (when the rich view is active). Watch out when activating OLE objects, these could contain malicious code. Of course a security warning is shown before activating these objects to remind you this fact.


Viewing meta data


Metadata is most commonly stored for file attachment icons. Selecting a message property containing metadata and setting the right pane to 'Rich View' will show the image contained in this property.

Date and time properties may also be viewed through the Rich View as the figure that follows illustrates.


Viewing date information



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Background on TNEF and MAPI messages

MS Exchange ver4 to ver5.5 encoded all mail messages using MAPI. In the versions that followed, starting from MS Exchange 2000, there was a clear shift towards the adoption of internet protocols such as SMTP. This naturally led the way to a broader support to MIME message encoding. Nevertheless, even with the latest Exchange versions, internal Exchange mails are normally always encoded using MAPI. To begin with the primary Exchange client MS Outlook is itself a MAPI client (i.e. it interacts with Exchange through MAPI interfaces and generates MAPI messages). 

MAPI messages (aka rich text messages) enable Exchange to provide a broad variety of functionality that go beyond mailing. It provides a flexible and extensible encoding system to consistently represent a wide variety of information. Apart for emails, MAPI messages are also used to encode contacts, calendaring data, notes and a lot more. All of this functionality makes it easier to understand why today Exchange 2003 still relies on a MAPI client as its primary client interface. 

The Transport Neutral Encapsulation Format, TNEF, is an integral part of MAPI. TNEF was created to encapsulate MAPI messages. As the name suggests it frees MAPI messages from the traditional MAPI transport providers rendering them "transport neutral". In simple terms TNEF enable MAPI messages to be transported over SMTP. 

A MAPI message when hitting an SMTP transport has two main options, either converting all of its content to standard MIME, or encapsulate itself through TNEF. Which of these options is adopted depends on the message recipients. If the recipient is one that supports MAPI then TNEF is the best option. The recipient would in this case receive the exact mail content as submitted by the sender. 

If the mail recipient is unable to handle MAPI messages then conversion to standard MIME is necessary. This conversion leads to loss of information. For example there exist many MAPI properties that have no direct equivalent in standard MIME. Also OLE objects, which in MAPI can be inserted within the mail content, cannot be easily represented in MIME. 


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Opening Microsoft Outlook *.msg mails

Viewing MAPI messages requires a MAPI client, such as MS Outlook, to be installed on the machine running WinDeveloper TNEF View. Follow these steps to open MS Outlook *.msg files:

  1. Save to disk the mails you want to view. From Outlook you can drag and drop mails directly to windows explorer. 
  2. Open WinDeveloper TNEF View.
  3. Open the mail to view from File | 'Open...' menu.

You may also follow the same procedure for other MAPI mail clients other than MS Outlook. 


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Opening TNEF messages (winmail.dat)

TNEF is normally embedded within SMTP mails as an attachment named winmail.dat. The following is the typical raw content of a mail containing TNEF. 


Extracting TNEF


This attachment effectively contains the entire mail content originally created by the sending end. Winmail.dat would include the original mail body and its attachments all encapsulated into one single file. 

On Windows2000 and higher open TNEF as follows:

  1. From your SMTP/POP3 client save to disk the mail containing TNEF.
  2. Open WinDeveloper TNEF View
  3. Open the mail to view from File | 'Open...' menu.


On NT4 open TNEF as follows:

  1. From your SMTP/POP3 mail client open the mail containing TNEF.
  2. Save the winmail.dat mail attachment to disk. 
  3. Open WinDeveloper TNEF View
  4. Open winmail.dat to view from the File | 'Open...' menu. 

Important note: Some mail clients, like Outlook Express, hide the content of TNEF attachments. To work around this limitation check the Troubleshooting section.


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Extract mail parts to an external file

One of the most powerful features of the viewer is the ability to save any part of the message to an external file. This enables you to easily extract mail attachments so as to view them in their appropriate viewer.


Saving attachment data to disk


Saving Attachments


Follow these steps to save an attachment to disk:

  1. Open the message in WinDeveloper TNEF View.
  2. Collapse the tree in the left pane exposing the properties under 'Attachment Attributes'.
  3. You will find the data for "normal attachments" under the \attAttachData\Data node.
  4. With the Data node selected as shown in the screen grab, select Tools | 'Save data to file...'.
  5. In the 'Save As' dialog that follows enter the attachment filename and click on Save.

The above procedure referred to "normal attachments". In MAPI, OLE objects and embedded messages are not saved in the location described here. Check the procedure for viewing embedded mail attachments for more details. Also note that 'Save data to file...' functionality may be used on any message property not just mail attachments.


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Viewing embedded mails (mails attached to another mail)


Embedded mails


Opening mails attached to another mail is different from opening normal attachments since MAPI saves these differently. Follow these steps to open embedded mails:

  1. Open the message in WinDeveloper TNEF View.
  2. Collapse the tree in the left pane exposing the properties under 'Attachment Attributes'.
  3. You will find the mail data under the \attAttachment\Property List\PR_ATTACH_DATA_OBJ\Value node.
  4. With the Value node selected as shown in the screen grab, select Tools | 'Open embedded Message'.

OLE objects are also saved in this manner. Lookup OLE objects by collapsing the same tree nodes. You may than save OLE objects to an external file using Tools | 'Save data to file...'. Otherwise you can view and activate these objects through the Rich View.


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Click here for the latest list of troubleshooting tips.


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Feedback and Support

If you are having any problems using this viewer check the Troubleshooting section for a list of the most common problems/solutions.

If the Troubleshooting tips still do not solve your problem, or you have any other feedback mail to:

If you are having problems with viewing a specific mail, make sure to attach this (compressed) to the support mail. 


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