I am having the reverse of the typical winmail dat problem. I have a mac with microsoft office installed. I am sending an excel template to windows users. The template was dropped/dragged (from my old windows computer) to my excel for mac. When the file is sent to any windows user they receive a winmail dat file. When I send it to myself it works fine. I want to be able to alter the file before sending so the very busy and not highly technical recipients can receive my emails. Hope you find this interesting and even better, find a solution.