Comment 8 for bug 200852

@Kyle
What settings are you using for displaying html-mail? I've recently observed that such attachment.dat files are shown in Evolution as attachments, when the messages consist of two different mime-types (e.g. text/plain and html/plain), and you've chosen to prefer text-display over html one.

Evolution does not show these files when you choose to prefer the html-content (the content should be the same, only the markup is different). I get such mails mainly from people using MS Outlook. When I was talking about tnef and winmail.dat files, I thought about attachments produced due to some misconfiguration in older outlook-clients, so this does not seem to be related to that what you are talking about.