Winmail.dat Files

My users are whining about these stupid winmail.dat files nearly every day. I usually use Kmail for my work related stuff, so I rarely have any problems with these. I simply use ktnef to extract the attachments and go on with my life. But since 100% of my user base is windows based and Outlook bound, this was not an optimal solution.

The problem occurs when an Outlook user sends someone an email with several attachments and he has either (a) HTML enabled, (b) attached vCard or (c) all of the above. If the recipient has a different version of Outlook, or uses a different client altogether, he is most likely to receive an email with a mysterious attachment called winmail.dat

Apparently winmail.dat is used to store the formating information for HTML enabled emails and/or vcards. Don’t ask my why – they just use it internally somehow. Another Outlook client is supposed to decode that file on the fly. Unfortunately, older version of Outlook often can’t read the dat files issued by the newer versions – and you get these mysterious attachments.

My advice, as usual it is: don’t use freakin outlook! But if you cant live without Outlook, just send messages in plain text, and never, ever attach vcards!

If some asshat sends you an email with winmail.dat here is what you do:

  1. yell at the asshat
  2. send him/her a tar file with a postscript document as an act of revenge (windows users are scared of postscript and tar files)
  3. use the TNEF viewer of choice to open the file and extract attachments.

Personally, I use ktnef. But if use windows, you might need to use something different.

For windows usage, I found a very obscure but functional command line tool called WMDecode. I guess an old rule of thumb is that good hackers are usually poor web designers… This guy must be a freakin genius then, because his website sucks! But the WMDecode tool actually works as advertised and its all that counts!

It’s actually really simple to use – you just drag your file onto the WMDecode.exe and poof – the attached files magically appear in the same directory. This way it’s not all scary and mysterious for stupid windows users 🙂


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