I am running Exchange 2007 on Windows 2003 R2 64 bit. End users run Outlook 2007 on XP sp2 machines. Users randomly receive winmail.dat attachments in their email. Does anyone know how to fix this on Exchange 2007?

Take a look at below article, which explains you what it winmail.dat and to fight with it. How e-mail message formats affect Internet e-mail messages in Outlook

Thank you for your post and the link with the information. I have read this article before. My take on TNEF and Microsoft Exchange isthat if your Exchange server receives mail form another Exchange server that it should recognize the TNEF encoding. In addition, all of my e mail clients are Outlook 2007 which should also recognize TNEF and decode the winmail.dat file. However this is not the case all the time. The only way I have been able to resolve the issue is report the problem to the sender and have them change their settings to send in plain text. This is a real pain in the butt when you have to contact 5 or 6 people a day. They use Microsoft Exchange and Outlook, I use Microsoft Exchange and Outlook; it should not be creating winmail.dat attachments. Does anyone have any other suggestions?

I'm having a similar problem in Exchange/Outlook 2003. Clients will at times receive a message on our Exchange server, read it with their Outlook client, and find only a winmail.dat attachment instead of the file they expected. Better yet, a different recipient on the same server may receive the same message (ie by being a cc recipient, or because both individuals subscribe to a particular mailing list) and have it presented correctly, with a usable file attached. The first time I saw this issue I resolved it by deleting the Exchange account of the user in question and re-creating it. However, I now have more users reporting the same issue and I don't believe this is really the "right" way to solve it. Can anyone help? Thanks!

Similar thing here, running SBS 2003 R2, and workstations are XP Pro, Office 2003... 1 user will send an email to outside the domain and the recipient receives a winmail.dat file rather than the email and attachment sent. But if another user sends the EXACT file to the EXACT recipient, it will deliver perfectly!!! Any suggestions are welcome, this is happening to only 1 person in the domain.

Yes, very similar situation. This does not happen when we send out mail, only incoming. I think I may have narrowed down what may have caused this for us: Our spam filter was a few versions behind (Trend Micro ISS version 5) when we upgraded from Exchange 5.5 to Exchange 2007. I upgraded Trend to 7.0 and the problem seems to have went away. One thing to note: If the mail recipient is not using a Microsoft TNEF compliant mail client, they may receive the winmail.dat attachment. See previous posts.

That is what I find most interesting, is what Microsoft has released regarding winmail.dat files. It seemed to me that it was the mail compliance of the recipient that was causing these files to appear. Only recently have I found more discussion on the topic on other forums, including here, showing that it is also caused by other situational basis other than the recipients method of viewing the email...unless I misunderstood all along and it would seem so. Because in my mind, it would make more sense if the recipients mail server is the cause of the issue, not so much the recipient. if the recipients mail server does not interpret TNEF than could all their customers be experiencing this? i must assume this because it would mean that if the recipient accesses their email via a webmail client that does not support TNEF, than they receive a winmail.dat...however if they check their email again from outlook or someform of email program that does understand TNEF, than shouldn't the email and attachments show up properly? It is my experience that they do not. That is how I began thinking that it must be the mail server of the recipient that is causing this. I tried setting the 1 user's outlook to send only plain text...I am waiting to hear the results, but they were already set to send in HTML only. By my understanding is that TNEF is created only when RTF is used for outbound email, and HTML and Plain Text do not create TNEF...punch me if I'm wrong