I have some users reporting this issue. An outside user send attachments to me, it comes through fine, jpg or zip, pdf etc. But if the outside user send it to this user internally, the attachment comes in as winmail.dat. This issue started occurring after I move from exchange 2003 to 2010.
I made sure the outside user is sending it as html because I got the attachment.
On the internal user that is getting winmail.dat file, I look at those emails and the format is all text file instead of html. There's no formatting or logos.
How can their account be forcing emails to text instead of html? But it might be a different email issue.
Our email scanning software is not related, was on with support and we turn off everything and test, still same issue.