Problem with Thunderbird

Fabian Rodriguez magicfab at
Wed May 16 18:05:07 UTC 2007

David Harrison wrote:
> [...]My issue: for some reason when MS WOrd 
> documents are sent to me as file attachments, all I get is a file 
> attachment called winmail.dat which (a) is not the file attachment that 
> was sent, and (b) I can't open anyway.
> However if I send myself a file attacment of an Open Office document, I 
> can openit properly.
Outlook and Outlook Express do this. It' s called Transport Neutral 
Encapsulation Format (TNEF), it's a proprietary attachment format.

 From :
"When an Outlook user composes and sends a message using either Rich 
Text Format or HTML Format, Outlook automagically generates a file, 
*winmail.dat*, and attaches it to the end of the message. *winmail.dat* 
contains formatting information, in a human-unreadable form, that 
Outlook will use on the receiving end to display this email message 
correctly. Unfortunately, Outlook is the *ONLY* email client program 
that can use this information! Netscape Messenger, Eudora^* 
<>, and other 
email client programs don't understand this information."

If you think the sender of the problematic email(s) may be receptive to 
this problem, you can try and have them follow instructions from this MS 
Knowledgebase article:

How to Prevent the Winmail.dat File from Being Sent to Internet Users

There' s also more information here:

And of course there' s an extension, for those cases where the sender 
can't or won't cooperate:

Let us know how /if this works out for you.


Fabian Rodriguez

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