After doing some reading in the forum and some experimentation; it appears that some users will receive the file in its original format and others will receive the winmail.dat. The cause appears to be whether the user is in either the To field or cc field. The To user received the attachment no problem, the cc user gets the winmail.dat.
Hope this helps.
Subject: winmail.dat characteristic
Yep, thats whats happening here too. Cheers!
Subject: winmail.dat characteristic
For some users using To fields I have also the same problem.
Subject: The problem is caused by the sender (was winmail.dat characteristic)
The reason that attachments show up as winmail.dat is because the sender is sending via Outlook and has the recipient listed in their (Outlook) address book as receiving e-mails in Microsoft Rich Text format. The only solution we have seen is to tell the sender to delete the reference to our user in their address book and re-add them without specifying that they are Microsoft Rich Text users.
it annoys us on a weekly basis, so we had a lot invested in figuring out what causes it. hth.
brandt