Winmail.dat attachments: Difference between revisions

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(→‎Disabling TNEF in Outlook: add basic explanation)
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Outlook uses the Transport Neutral Encapsulation Format (TNEF) to send messages with Rich Text Format (RTF) formatting. If your e-mail client doesn't support TNEF (most don't) you may also recieve a winmail.dat or a "Part 1.2" attachment. Sometimes you may receive an attachment with a generic name such as ATT00008.dat or ATT00005.eml instead. You can configure Thunderbird to use one of the programs below to open the application/ms-tnef attachment.
==Problem==
The Microsoft Outlook e-mail program sometimes sends e-mails in the Transport Neutral Encapsulation Format (TNEF). Most other e-mail programs, including Thunderbird, do not understand TNEF.
 
If your e-mail program doesn't understand TNEF, instead of seeing the e-mail and/or attachment, you may only see an attachment named '''"winmail.dat"''' or "Part 1.2" that you cannot open.   Also, sometimes you may receive a TNEF attachment with a generic name such as ATT00008.dat or ATT00005.eml instead.  
 
===Identifying TNEF attachments===
While almost all attachments named "winmail.dat" are TNEF, you could receive non-TNEF attachments ending in ".dat", ".eml" or labeled "Part 1.2".  In particular, AVG (an anti-virus program) can also add a "Part 1.2" attachment that contains the same information about the message having been scanned for viruses that it adds to end of the message body.
 
To identify for sure whether or not you've received a TNEF attachment, highlight the message and click "View" -> "Message Source".  Look for where the attachment begins; it looks something like the  following (these are the "MIME headers"):
 
--------------050804030404070201030211
Content-Type: application/ms-tnef;
  name="winmail.dat"
Content-Transfer-Encoding: base64
 
If you see "Content-Type: application/ms-tnef" then it's a TNEF attachment.  If you see another "Content-Type", then it's likely something else.
 
==Solutions==
You can configure Thunderbird to use one of the programs below to open the TNEF attachment.


* [http://www.fentun.com/ Fentun] Win9X, NT, and Win2K but not Windows XP
* [http://www.fentun.com/ Fentun] Win9X, NT, and Win2K but not Windows XP
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* [http://www.joshjacob.com/macdev/tnef/ TNEF's Enough] OS9 and OSX
* [http://www.joshjacob.com/macdev/tnef/ TNEF's Enough] OS9 and OSX


Note that AVG (a anti-virus program) can also add a "Part 1.2" attachment that contains the same information about the message having been scanned for viruses that it adds to end of the message body.
 


===Disabling TNEF in Outlook===
===Disabling TNEF in Outlook===
The sender can avoid sending a winmail.dat file by turning off TNEF in Outlook.  When Outlook is configured to send e-mail in "Rich Text Format", it uses TNEF.  When it sends in "HTML" or "Plain Text", it uses standard, compatible formats.
The sender can avoid sending a winmail.dat file by turning off TNEF in Outlook.  When Outlook is configured to send e-mail in "Outlook Rich Text Format", it uses TNEF.  When it sends in "HTML" or "Plain Text", it uses standard, compatible formats.


In at least Outlook 2002 (a.k.a. Outlook XP) and Outlook 2003, if it's being used at a business, the following is recommended to ensure compatibility with corporate mail systems:
In at least Outlook 2002 (a.k.a. Outlook XP) and Outlook 2003, if it's being used at a business, the following is recommended to ensure compatibility with corporate mail systems:

Revision as of 04:14, 7 March 2006

This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

Problem

The Microsoft Outlook e-mail program sometimes sends e-mails in the Transport Neutral Encapsulation Format (TNEF). Most other e-mail programs, including Thunderbird, do not understand TNEF.

If your e-mail program doesn't understand TNEF, instead of seeing the e-mail and/or attachment, you may only see an attachment named "winmail.dat" or "Part 1.2" that you cannot open. Also, sometimes you may receive a TNEF attachment with a generic name such as ATT00008.dat or ATT00005.eml instead.

Identifying TNEF attachments

While almost all attachments named "winmail.dat" are TNEF, you could receive non-TNEF attachments ending in ".dat", ".eml" or labeled "Part 1.2". In particular, AVG (an anti-virus program) can also add a "Part 1.2" attachment that contains the same information about the message having been scanned for viruses that it adds to end of the message body.

To identify for sure whether or not you've received a TNEF attachment, highlight the message and click "View" -> "Message Source". Look for where the attachment begins; it looks something like the following (these are the "MIME headers"):

--------------050804030404070201030211
Content-Type: application/ms-tnef;
 name="winmail.dat"
Content-Transfer-Encoding: base64

If you see "Content-Type: application/ms-tnef" then it's a TNEF attachment. If you see another "Content-Type", then it's likely something else.

Solutions

You can configure Thunderbird to use one of the programs below to open the TNEF attachment.

  • Fentun Win9X, NT, and Win2K but not Windows XP


Disabling TNEF in Outlook

The sender can avoid sending a winmail.dat file by turning off TNEF in Outlook. When Outlook is configured to send e-mail in "Outlook Rich Text Format", it uses TNEF. When it sends in "HTML" or "Plain Text", it uses standard, compatible formats.

In at least Outlook 2002 (a.k.a. Outlook XP) and Outlook 2003, if it's being used at a business, the following is recommended to ensure compatibility with corporate mail systems:

  1. On the "Tools" menu, click "Options", then click the "Mail Format" tab, and then the "Internet Format" button.
  2. Set "When sending Outlook Rich Text messages to Internet ..." to either "Convert to HTML format" or "Convert to Plain Text format".


In all versions of Outlook, you can disable TNEF completely:

  1. On the "Tools" menu, click "Options", and then click the "Mail Format" tab.
  2. In the "Send in this message format" list, click "Plain Text" or "HTML", and then click "OK".

External links