One of the first problems I encountered when using my new Mac was receiving email attachments 
I had emailed myself from my PC a standard Microsoft Word document. It mailed to my mac, and I opened it in Microsoft Outlook. The attachment however showed the document as winmail.dat. It should have shown up as Essay.doc. When I tried opening the winmail.dat program, I had to navigate to Microsoft Word on my computer to try to open it. When I opened the file, it just showed a bunch of gibberish writing that was unreadable.
I was confused. Why could I not send a Word document through Outlook, to be opened by another computer using Outlook and Word? I looked online for answers and found people recommending I purchase some converter programs that would make the winmail.dat file read correctly. I didn’t feel that this had to be the only way, so I kept searching.
I finally stumbled on a solution that worked for me, and as a bonus was really easy. What I had to do was go to Outlook on my PC, and delete myself as a contact. I deleted myself, then resent the email with the .Doc attachment, this time manually entering in my email address as if it was the first time. I sent the email on. Lo and behold, when I received it on my Mac it was in the normal .Doc format that I wanted. I was able to then easily click on the attachment and open it immediately in Word. This was a quick and easy way to solve my problem. The only potential problem I see is that sometimes I receive emails from clients who might also send me the winmail.dat file inadvertently. I will have to either continue to research this problem and discover the root of what is going on so I can develop a permanent fix. Or, if the problem is infrequent I could always send a polite email to my clients asking them to delete me and re-add me to their address books.