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How to revert winmail.dat attachments to original content Apps
Firstly, I guess this isn't solely Mac specific and can actually help any email user as we will see, but Mac users would be an ideal target. Secondly, to be honest I don't know all the circumstances that cause the problem I am about to solve, but if you have ever used Outlook as your mail client you are probably aware of the infamous winmail.dat.

Dependening on one of those annoyingly obscure configuration options and set on by default, when Outlook creates a message it stores all the text formatting information and any real attachments into a single attachment called winmail.dat. In Outlook itself, this file is decoded transparently and the messsage appears normal to the user (i.e. you don't know of the existence of the file). To everyone else, the message is actually just plain text and there is no direct access to the real attachments as they are embedded in the now visible winmail.dat attachment.

So, the first part of the hint is a warning to help prevent the build up/creation of these messages (to be fair, I am not sure if Outlook 2003 still creates them). When I first switched, I was using POP so had a lot of mail stored locally within Outlook. When wanting to move the messages to my Mac and searching this very site for the best method, I opted for the seemingly easiest method of using an IMAP server as a transport - i.e. copy from my Outlook local folders to an IMAP remote folder then download to Mac using the same IMAP connection. This is still a sound theory, but unfortuantely any message in Outlook that is in the winmail.dat format will remain like that after the transfer (and it seems impossible to know which). Therefore, when complete, you will likely have many messages on your Mac where access to the real attachments is lost, as they are actually embedded in the previously invisible winmail.dat file. (Also, any mail that had no real attachments originally but even minor formatting (such as a bolded word) will now have a single attachment just for the sake of containing information on formatting.) Once you have these, to view the real attachments you have to get other programs to decode the winmail.dat afterwards, which is not really very convenient plus requires a third party application. So, the warning here is to not use Outlook to transfer messages via IMAP.

So, how should you transfer these messages if they are in Outlook already AND in the wrong format? Turns out that Outlook Express, which should be on every machine that has Outlook, is also able to decode the winmail.dat messages transparently like Outlook, but it does not create them! So, if you import the messages into Outlook Express from Outlook they will appear perfectly. More importanly, when using Outlook Express to transfer via IMAP it leaves them in the decoded state so the messages will have ALL the correct formatting, and ALL the real attachments!

The above sounds sensible enough, but the real benefit of the process (and the beauty of this hint that I could not find anywhere else on the interweb) is that if you have already mistakenly moved a bunch of mail using the Outlook IMAP method previously, and now have a bunch of mail with winmail.dat's, you can use this method to convert them back to their original format! Simply put them back onto an IMAP server, connect to that server using Outlook, then copy the mail locally. They will now be in Outlook and will look correct once again due to the auto decode. Now open Outlook Express and import the mails in question from Outlook. Finally, use an IMAP connection in Outlook Express to copy back to the server. Outlook Express will create decoded messages on the Server and all the winmail.dats will be gone forever!
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How to revert winmail.dat attachments to original content | 8 comments | Create New Account
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How to revert winmail.dat attachments to original content
Authored by: rwinchester on Aug 25, '06 07:54:16AM
A recent-switcher friend of mine just wrote yesterday with this problem, and I found an easy solution online: Josh Jacob wrote a freeware converter called TNEF's Enough. It works perfectly on any Winmail.dat attachment. So... cheers to guys like Josh who do all the research on this stuff and release their work for free. That is why the Mac community is awesome.

http://www.joshjacob.com/macdev/tnef/

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How to revert winmail.dat attachments to original content
Authored by: killermink on Aug 25, '06 06:06:40PM

Yeah, I have seen a couple of conversion programs, but as far as I know while they can open the attachments they don't save it back to the email do they? I got into a situation where I was on many computers and didn't want to have to keep installing other programs to view attachments.

Also, I don't think the programs decode the formatting part of the messages. 9 times out of 10 it doesn't matter, but I for one like to see such eyecandy!



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Not perfect
Authored by: bonkydooky on Aug 25, '06 08:53:44AM

TNEFs Enough might be worth a try, but I found that it doesn't work for everything.



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How to revert winmail.dat attachments to original content
Authored by: machard on Aug 25, '06 10:20:53AM

I believe that winmail.dat files are created when Outlook is set to create emails in Rich Text Format. Simply changing to plain text or html should solve the problem.



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How to revert winmail.dat attachments to original content
Authored by: fungus on Aug 25, '06 12:14:38PM
Applications like TNEF's Enough are great, but this doesn't help the real problem. We need to prevent these files from being created in the first place.

Every time you get one, reply to the sender explaining that the attachment was sent in a Microsoft only format. They should send the message again in a format that is readable by the rest of the world. Also reference their own KB article. http://support.microsoft.com/kb/138053/EN-US/

Hopefully they will get a clue for future recipients of their messages.

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How to revert winmail.dat attachments to original content
Authored by: wsdr on Aug 25, '06 02:48:58PM

The solution for never receiving these attachments is, alas, out of your hands. However, you should do the following: tell your Outlook using friends to go into their Contacts and mark your contact to receive plaintext mail. Problem solved. Of course, that assumes your Windows using friends are savvy enough to find the setting, and not too stubborn to do it (ha).



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How to revert winmail.dat attachments to original content
Authored by: killermink on Aug 25, '06 06:10:55PM

To be honest, since I've switched I have never seen this problem for new mail. For a few years I have had really old messages in my Inbox with the winmail.dat's and just recently found some time to try the method I explain to convert them. So, for me at least the problem was with my Outlook when I switched, and not other peoples!



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How to revert winmail.dat attachments to original content
Authored by: mat79 on Aug 26, '06 09:28:28AM

usually this is not an outlook problem, but an exchange server misconfiguration, so telling the user wont help much.

(but in Exchange 2003, the default setting is to not send winmail.dats, but to convert the mail to HTML before sending)

BTW: if you are migrating from Outlook to Mail.app or something else, you may want to first migrate from Outlook -> Thunderbird (on windows). TB does have an Outlook importer (that doesnt create winmail.dat) and you can import thunderbirds mbox files into Mail.app (and most other apps)



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