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What is that winmail.dat file? - 01/19/07

From: Email Guy
Subject:       What is that winmail.dat file?
Date: January 19, 2007 4:29 PM
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User ALWAYSMILEN3 posted the question below in the Ask Email Guy section, and I since this is a very common issue I decided to publish my answer up front here for everyone's benefit. This problem has been around for years now and still frustrates people who receive email from users of the various flavors of Microsoft Outlook.


Posted by: ALWAYSMILEN3 | January 19, 2007 11:49 AM | (228)

My somewhat acerbic response (not at the user) is below:

Alwaysmilen3 - I'm going to break one of my published rules here and give you some help with your MS Outlook software, because this issue is a real pet peeve for me.

That winmail.dat file isn't created by Web Mail. It is a file that is created by Microsoft Outlook and Microsoft Exchange, and it is only understood by them. Learn more about it here.

In Microsoft's infinite wisdom they found it necessary to send attached files in a proprietary format rather than use MIME like every other email software in the world does. You can stop this from happening by changing the settings in those MS programs, so that when email is received by a non-Microsoft email reader (like our Web Mail) you won't get a useless winmail.dat file but instead you'll get the real attachment in its original format.

Here's Microsoft's explanation and fix for it: http://support.microsoft.com/kb/290809

You'll see them calling this a TNEF format like it is a real standard that other email programs are supposed to understand, but the fact is they entirely made it up and expected the world to support it (or force everyone to use Outlook). In fact, the full name of the format is MS-TNEF. The real standard in use by the rest of the universe is called MIME. Anyway, they tell you how to fix the problem there. Look down to the section that says "How to Specify E-mail Format".

There are also some freeware decoders you can download for those winmail.dat files. Find them on Google.

I generally like and use MS stuff, but winmail.dat has always irritated me in particular since I've never been an Outlook user. Since I felt the need to speak out on this topic, I probably should emphasize my disclaimer here (which appears elsewhere on this blog) that this comment is my opinion, and doesn't necessarily represent the position or opinion of EarthLink.

Ed. Note - Frequent commenter Bob corrected me in the comments below, pointing out that Outlook Express does not create these files, it is only Outlook and MS Exchange. Outlook Express can't read these messages either, and it doesn't even show you the winmail.dat, it just ignores it entirely. Correction has been made above to not include Outlook Express as one that creates these files.


Posted by: Bob   |   January 20, 2007 11:02 PM    |   (1)

Hi Email Guy,

I see that you've posted this on the opening page of your Webmail Blog, and I thoroughly agree with your sentiments about winmail.dat files. You just ought to correct a minor misstatement at the beginning of your piece, where you wrote that this kind of file "is created by Microsoft Outlook and Outlook Express, and it is only understood by them." Actually, as pointed out in both of the references you cited, such files are created only by Microsoft Outlook and Microsoft Exchange server but not by Outlook Express. The Microsoft reference also points out that when an email containing TNEF information is received in Outlook Express, it "does not understand TNEF, but it does know to ignore TNEF information. The result is a plain text message."

Of course, it can look pretty strange if you receive a 5 MB email in Outlook Express (which you can tell if you've set it to display a "Size" column in your Inbox) but all you see is a short text message that ought to occupy just a few kilobytes. The only way to figure out what happened in that case is to view the raw Message Source, which can be done in Outlook Express, although it takes several steps. Incidentally, if you're using Outlook, you can't view original message source because Outlook doesn't preserve received messages in their original format (and I believe this is true of Eudora too). I'm happy that Earthlink Webmail allows viewing original message source ("View Email Source" link in upper right of webmail window).

Posted by: Email Guy   |   January 21, 2007 10:59 AM    |   (2)

Thanks Bob, you're correct (I verified it by testing) and I'll fix the post.

Posted by: JayPel   |   January 29, 2007 6:45 AM    |   (3)

-- Useful information such as you provided, re TNEF, Winmail.dat, MS Outlook, etc. is very helpful. It may be useful down the line to collect this kind of information into a FAQ section for Earthlink mail users -- accompanied by cleaning out or archiving deeper the blog chat message threads that support the FAQ entry.

-- It's easier & quicker to find needed concise information posted to a FAQ list rather than have to plow thru lengthy chat/mail/msg threads. (Loose "data" is organized into useful "information" in a FAQ.)

-- The deeper archived message thread material could be made available via hyperlink from the FAQ entry as supporting material for deeper research and/or reviewing for update of the FAQ entry.

Posted by: Email Guy   |   January 29, 2007 7:58 AM    |   (4)

Hmmm.... , if you look on the left side the main page in this blog, you'll see FAQ there. And clicking that opens a listing of all of the entries that I have designated in that category, in an easy to scan list where you can open the one you are looking for. Is that kind of what you meant? Seriously, I'll see if I can make it easier to find.

Posted by: JayPel   |   January 29, 2007 11:33 AM    |   (5)

-- Thanx for keeping me straight. I perhaps jumped in too quick after first discovering the "Web Mail Blog" from it's publicity headline on the web mail login page (just today).

-- A couple of things that may have averted such first time behavior:
--- include reference to FAQ item at beginning of new blog items that elaborate on and/or update information in FAQ entries (hyperlink to the referenced item would be nice);
--- make the FAQ hyperlink on front page a little more visibly prominent so as to catch the eye upon entry; and,
--- include links to the FAQ from other locations in web mail country where users might be expected to seek help -- such as within or next to "Web Mail Help" hyperlink on user logged-in page.

-- I presume that the FAQ entries are indexed to ease finding via Google type search box on web mail site.

Posted by: Email Guy   |   January 29, 2007 11:38 AM    |   (6)

Thanks for the suggestions, I agree about making the FAQ more prominent. As for the searching, every word on every page is searchable by specific words or phrases, including support for AND and OR and regex, using the Search built-in to the blog. However, I'm working on improving the search template too, especially with the long paginated threads. I should have some updates to both this week.

Posted by: Deanna Mosler   |   March 9, 2007 10:01 AM    |   (7)

I've a suggestion on a link highlighted at the top of webmail items. The "This is Spam" link is placed such that I've hit it inadvertantly and then had to scramble to undo my mistake. Could this be placed farther to the right and perhaps boxed like a radio button instead of being out in the middle and near the Reply buttons to help avoid such problems?

Posted by: Thomas   |   March 26, 2007 5:28 PM    |   (8)

One way to solve this winmail.dat problem lis to use an online converter like http://www.winmaildat.com . Of course, this is still a pain if you get a lot of those attachments.

Posted by: badrinarayanan   |   March 31, 2007 3:48 AM    |   (9)

I want to know how to get the original mail with complete original header information of a mail that is received in a webmail.

in gmail we use show original option.


View Email Source. You can also use "View All Headers" to see only the headers and not all the content and encoded attachments. Both options are at the top of the message view, or the bottom of the preview.

Email Guy

Posted by: Jorrit   |   October 2, 2007 5:21 AM    |   (10)

I checked the Microsoft URL given in the Blog, followed the instructions and.. it did not work. Later I saw that the instructions are meant for Outlook 2003 of 2002 standard edition while I use the 2002 professional edition and there is no instruction for this version. I found the winmail.dat Reader and that is a useful tool. But maybe the real solution is to use freeware or open source e-mail programs.

Posted by: james   |   November 22, 2008 5:54 AM    |   (11)

thanks to Posted by: Thomas | March 26, 2007 5:28 PM | (8)

the link you post works a treat. Have good rest of the day

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