I have MS Win XP with SP2 installed on my computer and I use Microsoft Outlook 2003 as my email client. I have a vendor I work with that uses a macintosh running OS X and using Microsoft Entourage as her email client. When I send attachments, they usually end up as winmail.dat files on her end, be excel, word, or just about any other type of document. The odd thing is that this only happens to me when I send to her, and she only has problems from the mails I send. I've resorted to attaching mails in yousendit.com, but this is quite annoying sometimes.

Any ideas as to what settings could be affected, or what we could fiddle around with to fix this problem?