[Evolution] attachment.dat: pptx showing as plain text attachment

[Carpetnailz <carpetnailz researchintegration org>]

My wife sent me a power point file from her Mac using Mac mail but it
came through to Evo 3.8.5 on Fedora 19 as a plain text attachment called
attachment.dat that Evo wanted to open in gedit. What's happening here?

On line I find discussion of things arriving at .dat files from Windows
operating systems, but why would this happen from Mac Lion using the
default Mac mail system? It doesn't happen when she sends the same
attachment to my Win 7 box. And she's sent me Word and PowerPoint files
in the past without this problem.

Thanks.