Receiving the winmail.dat attachment?

The problem!

Over the past few months, we have seen several of our clients receive the ol’ winmail.dat attachment. Try as they might, they can’t open it. Frustration over the inability to open the email has even led several users to download some of the spam-ware applications claiming to open any file type. We know what happens then…

So, what is happening here?

From what we’ve been able to determine, there is an issue with the mail servers properly decoding the email between the sender and recipient.  I’m placing the blame on Outlook because it will use either RTF or HTML formatting of the message content.


We spent a lot of time digging into the problem. We tried making changes as recommended in Microsoft Knowledgebase Article Q138053 but with no success. We’ve tried changing the formatting in Outlook but this seems to be ignored also.  We had come under the gun a couple of times because we maintain the receiving exchange servers. Spending countless hours updating settings in the servers we managed push me to think the issue could reside on the sender’s side. There was one thing that caught our eyes in the Microsoft KB article: you could adjust the message type based upon contacts.  Contacts?  According to quiet a few of our customers, contacts are the names that automatically drop down when you start typing a person’s email address!! This gave us an idea and led us to the solution.

How do you fix it?

We all love the cached contacts that Microsoft graciously implemented in Outlook. I use it every day as does all Outlook users. It looks to me that maybe somewhere, the formatting of the email is being maintained along with the cached address.  We can’t delete the NK2 file or flush the complete cache. So, how about removing the problem recipient’s cached address?

  1. Open a new email message.
  2. Begin typing the problem recipient’s address until you see it listed in the drop-down.
  3. Use the cursor keys until the address is highlighted.
  4. Press the delete key on the keyboard to remove the address.
  5. Now, type the full email address in the TO field.
  6. Finish e-mail and Send.

Your message should now be in the mailbox, in its proper format, of the problem receipient.

Your Ideas

Please feel free to comment if you can shed any more light on this subject.

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