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Mac OS X clients getting WINMAIL.DAT files, just not the way you expect...

tregas asked
Last Modified: 2012-05-10
Here's a simple and interesting one. Two users, both Mac OS X 10.6, both accessing Exchange 2007 server. One sends another an attachment. The recipient receives the attachment as a WINMAIL.DAT file, as if it were coming from a Windows client like Outlook Express and from the early 2000's.

Thoughts on why this is happening? How to stop it?

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I would suggest installing the latest updates for Exchange 2007.
If you are using Entourage, DO NOT install the latest Office update as it will cause crashing.


@dmessman --> I know of the issue you indicate, and this one's not it. This is a Mac sending to a Mac, both using Mail.app. They don't send in RTF, so it shouldn't be encoding the message in WINMAIL.DAT.

@OxygenITSolutions --> That I'm working on. Having come into this situation without having had hands on before is the primary complexity. I also generally refuse to deal with SBS, but either I do or I don't work. Period. I have SP3 on standby because one of the project managers says they are in a huge deadline crunch until the middle of November.

I love the fact that all businesses rely on technology to operate, but when it comes to making IT a priority, projects always get shoved to the bottom of the totem pole. They complain to me of an issue, but I can't apply the fix to that issue without them complaining.

Anything else I can look at which might be at issue before going to SP3?

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Thanks, guys! I don't think I'll be able to patch soon, but I will update this thread ASAP and let you know.
Dave MessmanIT Consultant

on the contrary - they are sending in RTF.  That's where winmail.dat attachments come from - RTF formatted emails being received by non-Outlook clients.


Mail.app does not generate RTF. Instead, it uses plain HTML for formatting. The issue is sending email from a Macintosh machine, through Exchange 2007, to a Macintosh machine. If it starts as HTML, it should arrive as HTML, unless Exchange is doing something on the way.

If I am unnecessarily re-clarifying, please forgive me :)

Dave MessmanIT Consultant

the point of the blog post was that even though you're sending in HTML or plain text, it arrives as RTF.  I advise you to check and confirm.


My bad. I get you now. Thanks :)

I figured it out, though it still needs to be tested. Using Exchange 2007, you need to do the following:
  1. Open the Exchange Management Console
  2. Expand the Organization Configuration option group
  3. Select Hub Transport
  4. Select the Remote Domains tab
  5. Get Properties for Default
  6. Select the "Format of original message sent as attachment to Journal report:" tab (I can see how that should have been obvious to me all this time!)
  7. Change the Exchange Rich-Text Format option to Never, or whichever option suits your needs.
I would not have found this were it not for your leads :) Thanks! Now, to see if it actually works.
Alan HardistyCo-Owner
Top Expert 2011

This question has been classified as abandoned and is being closed as part of the Cleanup Program. See my comment at the end of the question for more details.

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