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"winmail.dat" attachments are driving me nuts!

Dave, there are a couple of people who send me email, and, consistently, their attachments don't show up as neat "foo.doc" or "report.xls" but as the generic attachment winmail.dat. They don't know why and I don't know why. Worse, as a Mac user, I can't figure out what to do with them. What's causing these "winmail.dat" files and how do I decode 'em?

Dave's Answer:

I too have variously been plagued with this winmail.dat affliction, and as far as I can tell, the problem is that Microsoft Exchange servers use the mysterious winmail.dat method of encoding attachments that are sent from one Microsoft Outlook user to another through a Microsoft Exchange server.

Of course, you clearly aren't using Microsoft Outlook for Windows (since it would have magically decoded the attachment, leaving you none the wiser), and are instead faced with trying to decode this mysterious attachment...

Again, from what I've read, the real fix is for the sender to make a few tweaks to their Microsoft Outlook to ensure that their copy of Microsoft Exchange doesn't think it's sending to another Outlook user. It's easy: they just have to indicate in their address book entry for you that you cannot receive Rich Text Format (RTF) rather than the current setting which assumes that you can and therefore must be running Outlook! Getting your colleagues to change their address books so that you have an easier time with their attachments might be, um, a bit tricky, however. :-)

To simply unpack the attachments on your Mac, pop over to VersionTracker and search for "winmail.dat". Surprise! You'll find a link to a great little freeware app called TNEF's Enough from Josh Jacob. Download and install it and you'll be able to drag and drop these annoying winmail.dat files onto the app and have them unpack without incident.

Update: there's a nice new program called OMiC that not only helps you with your winmail.dat TNEF attachments, but has a bunch of other neat tricks up its sleeve too, including iCal event conversion and more. Please check it out!

That should solve your problem, or at least help you keep a tenuous grip on your sanity! Good luck.

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Categorized: Mac OS X Help (Article 3936)
Tagged: email, microsoft outlook, omic, winmail.dat
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Comments

Dave, thanks for this piece of information!

What a great title, too -- so apt!

Cheers,
Harris

Posted by: Harris Ueng at August 2, 2005 7:25 AM

In your solution for "winmail.dat" attachments are driving me nuts!, you said "indicate in their address book entry for you that you cannot receive Rich Text Format (RTF)". I could not find that setting for address book entries.
Thank you.

Posted by: Gerry Lavender at August 30, 2005 11:34 PM

Dear Dave - I read your solution to a MAC user about "winmail.dat" attachment files that drove him crazy. I have a professor who keeps sending us attachment with DAT extensions and it drives me nuts trying to decode them. So far no luck and I keep having to go beg for copies from class mates who can get decoded copies w/o any problems. Do you know of an app. similar to TNEF's Enough for PC users. Apprciate your help. Cheers, Robert

Posted by: Robert Bulham at September 2, 2005 5:19 PM

I popped over to http://www.download.com/ and did a search for "winmail.dat". Here are two that look like strong possibilities for you, Robert:

http://www.download.com/AkeeSoft-WMViewer/3000-2369_4-10383013.html?tag=lst-0-3

http://www.biblet.freeserve.co.uk/

I bet one of those will help you out!

Posted by: Dave Taylor at September 3, 2005 6:24 AM

Thank you so much for the TNEF tip. It works brilliantly.

Posted by: Giles Becket at October 7, 2005 12:32 AM

Thank you for your help, Dave. The applette at http://www.download.com/AkeeSoft-WMViewer/3000-2369_4-10383013.html?tag=lst-0-3 worked like a charm

Posted by: Robert Bulham at October 13, 2005 11:05 AM

I have been unable to access Josh's page to download the TNEF application. Safari keeps saying it can't open the page. Help?

Posted by: Kathleen van Graft at October 25, 2005 4:20 PM

The TNEF application doesn't seem to work for me. I have OS 10.4, and when I copy the winmail.dat file to the finder it takes on a Graphic Converter icon, but no files appear in the TNEF window that opens when I drag the file on the TNEF icon.

Posted by: Alfred de la Torre at November 10, 2005 4:16 AM

Alfred, right click (oops, sorry, Cmd-Click) on the .dat file and it should show you "Open With..." and you can pick the TNEF application. To permanently change this, choose Get Info from this same contextual menu, then change the Open With to be the TNEF application and click on "Change All.."

Posted by: Dave Taylor at November 10, 2005 6:33 AM

Thanks Dave, I got it to open TNEF by clicking on the icon, but I still get no files to appear in the Embedded Files window. Might this drat file (I mean dat file) just not have any embedded files?

Posted by: Alfred de la Torre at November 11, 2005 1:11 AM

Alfred, that's entirely possible, actually. Check the file size, and ask the person who sent it if there was an attachment included?

Posted by: Dave Taylor at November 11, 2005 7:05 AM

Yep, its only 12 kb, not much of a file! Thanks for your help.

Posted by: Alfred de la Torre at November 13, 2005 2:41 PM

I have the reverse of the winmail dat problem, and am still working the problem. You may find this interesting or better yet have a solution. I have a mac with office for mac. I am sending an excel template which was drop/drag to my mac excel program. I send the file and it ends up as winmail dat at all windows recipients. I would like to be able to fix the problem on my side (mac side). Driving me a little crazy at this point.

Posted by: Matthew Huennekens at December 3, 2005 2:11 AM

I've had this problem, too. In reply to Gerry Lavender at August 30, 2005; here's what I'm trying today:
(I use Windows ME) In my Outlook (2000) address book, right-click on the addressee's name and select "Properties." Go to the "Name" tab and then check the box "Send Email using plain text only" in the lower left corner.
I'll let you know...

Posted by: Paul Greer at March 4, 2006 10:40 AM

And thanks for having this site-
it's an excellent public service!

Posted by: Paul Greer at March 4, 2006 10:46 AM

TNEF's Enough works just as advertised, thanks, except that my Mac has a nag-ware copy of GraphicConverter hard-wired to load "winmail.dat" files. The "Open with ..." trick works to switch single files to TNEF's Enough, but if I try to "Change All..", it magically reverts to GraphicConverter. Which can't handle the file. And which, since I have no need for it and haven't bought and registered it, insists on posting a modal splash screen with an ever-lengthening nag-ware timer to encourage me to pay for this thing I don't want anyway but that insists on reinstalling itself even when I try not to run it.

Can you tell me how to un-wire GraphicConverter? It's actually a fine tool (I've used it in the past, but no longer have the need). But this trick of forcing itself upon me just so it can nag at me is geting extremely annoying!

Posted by: Jack at June 10, 2006 1:01 PM

Hi Dave ,
i have my own painting company, one of my clients sends me plans with winmail.dat.
My computer programs don't open them the computer is a toshiba harman/kardon.can you please advise me on a program that i can download or buy.
thank you very much Peter.

Posted by: peter dawes at February 13, 2007 12:46 AM

You can also use filejuicer to extract those pesky windoze files:
http://echoone.com/filejuicer/

Posted by: David Giorgi | Click here for Expat France at March 26, 2007 8:08 PM

Thanks Dave, the TNEF solution works perfectly. I appreciate your help!

Joel

Posted by: Joel Melashenko at April 3, 2007 10:07 AM

I'm using Mac OS X 10.2.8. The TNEF works for some files but not others. When I tried to open one winmail.dat using TNEF's Enough Carbon (version 1.0), it said Error! And I tried downloading the version 2.0 of TNEF, but I couldn't get the application to open. Finally, the OMiC software doesn't seem to be supported by the computer. What seems to be the problem? Is it the file, which is in pdf format?? Thanks

Posted by: maila at April 13, 2007 5:47 PM

It still works - this time on OS 10.4.9
made me very happy; though I had to go into TNEF's Enough and find and open the saved attachment from there. Maybe it'll be more automatic (i.e. open on double-clicking the attachement in Entourage) later... still ahppey a sis.
Many thanks to the developer and earlier commentators.
Paul

Posted by: paul at April 29, 2007 3:03 AM

Sometimes an online converter is the fastest way to open those attachments, for example www.winmaildat.com.

Thomas

Posted by: Thomas at April 30, 2007 12:54 PM

what about att####.DAT files.

I have trouble sending email with attachments to outlook users (sometimes). I do not use Outlook. Sometimes they receive the attachments fine, others they get changed to a .DAT file

Posted by: maslow at May 1, 2007 9:13 AM

Thanks for this, in 60 seconds I was back in business. Elegent little program. Now if they only had one for the folks in my office on PC's that seem to get DAT files from me.

Posted by: Kevin at May 31, 2007 5:44 PM

Here is a free program that opens the winmail.dat file for Windows.

http://tinyurl.com/2w4cn7 Winmail Opener

Posted by: Charles at January 7, 2008 5:27 PM

I tried downloading both OMiC, and TNEF's Enough but I can't get either of them to work in Mac Leopard (10.5). Any Suggestions?

Posted by: Andy at January 19, 2008 9:51 PM

When ever my dad or I get an e-mail with a .dat file attached to it, we can't read or open the .dat file to view its contents. Any sugestions on where we can find a viewer to view these files with after we download them?

Posted by: Craig at February 22, 2008 3:52 PM

Dave, you've come through again for me. The internet is a better place thanks to you.

Posted by: Bryan Azorsky at April 7, 2008 12:55 PM

I have a lot to say, but ...

I have a lot to say, and questions of my own for that matter, but most of all I'd like to say thank you for all your efforts on this Web site by buying you a chai!

I do have a comment, now that you mention it!