Winmail.dat files in Outlook 2007


OSNN Addict
4 Feb 2004
Hi guys,

We're currently using Exchange Server 2007 as our mail server & Outlook 2007 / Outlook Web Access 2007 as our email client.

Occasionally, one of users will receive an email from an external user with an attachment as a winmail.dat file. The winmail.dat files is (apparently) created when an email is created using Outlook as the email client. The file allows Outlook users to send Transport Neutral Encapsulation Format (TNEF) information along with the email so that it retains the look and feel of the document with formatting, fonts and colors when its received by another Microsoft Outlook user.

So why would our users, who are all using Outlook receiving winmail.dat files rather then the original attachments. We know that the files are legitimate & that they contain no virus/trojens.

Any help would be appreciated.


The problem is with Outlook RTF files, which was a very dumb implementation on M$ part


You can send emails in 3 mods (Plain Text - the best !), HTML (The 2nd best but won't work for everyone, and the worst (Rich Text, which may work if the moon and stars are aligned correctly and you see bigs flying out the window].

There are basically 2 options

1) Change your Outlook clients to only send plain text or HTML emails

2) Change your Exchange Server to automatically convert emails to Plain Text/HTML when passing through the internet mail connector. I'm pretty sure the setting is in the internet mail connector settings, but it's been a little bit since I've administred exchange.

Inside the WINMAIL.DAT is the information that outlook is supposed to read to produce the RTF email, but somewhere along the internet email headers or something may get stripped off and outlook ends up just seeing it as a regular attachment


I'm aware of what the winmail.dat is and how/why it is created. However, Outloook to Outlook email this should not happen. As our recipient user is using Outlook, the attachment should 'decode' correctly but it is not doing. That's what I can't undestand.


But you are talking about the message being sent over the internet right?

If you just mean within the same exchange server, then I agree this should not happen.

But it will happen over the internet for several reasons

1) M$ is not sending a standard email packet when they send the RTF information

2) Using Word as your email editor/reader makes some rather quirky assumptions when opening an email message

3) An internet message maybe delivered throuh several smtp hosts before it reaches it's desitation. Each time, an SMTP server may add header information to the message that confuses outlook.

4) The recieving outlook user, although they have outlook maybe in internet only mode (and not connected to an exchange server, or connected to a different mail server, that just sends the message as standard MIME attachment)

The Lesson: When writing mail clients and server software - stick to the RFC's

Sorry - I'm justing having a ranting day I guess!
Oh, and if the message is sent over X500 (exchange server -> exchange server) you should not see the attachment either, so long as it does not pass through SMTP you should be allright
Thanks again.

I am talking SMTP traffic over the internet. So basically, If I understand you correctly, the message is getting screwed up along the way somewhere so that Outlook can't identify it properly?

Though I feel it important to point out that the "messed" up part is happening because the orginal message (in RTF) is not following proper internet standards when it is sent.

The systems recieving the message are just doing their best to interpret the message; and that is to assume an attachment (WINMAIL.DAT) is trying to be sent with the message (which is the way it looks to any mail server)

Members online

No members online now.

Latest profile posts

Also Hi EP and people. I found this place again while looking through a oooollllllldddd backup. I have filled over 10TB and was looking at my collection of antiques. Any bids on the 500Mhz Win 95 fix?
Any of the SP crew still out there?
Xie wrote on Electronic Punk's profile.
Impressed you have kept this alive this long EP! So many sites have come and gone. :(

Just did some crude math and I apparently joined almost 18yrs ago, how is that possible???
hello peeps... is been some time since i last came here.
Electronic Punk wrote on Sazar's profile.
Rest in peace my friend, been trying to find you and finally did in the worst way imaginable.

Forum statistics

Latest member