I just upgraded Office 2007 to Office 2013 on the server that has Discover Manager 6.8.0.4127.  I was going to straight to 2016, but I wanted to make sure it would work with 2013 first.  After the upgrade, I went to a collection and was able to view the messages in the preview window.  However, when double-clicking on the message itself, it would give me the error "No supported email client was detected for native viewing". 

I checked Default Programs and Outlook is set to open .msg files.

I have no problem opening Outlook, then opening a PST file to view the messages (PST exported from DM)

I'm currently on version 6.8.

Is Office 2013 not supported with 6.8?   I don't think there aren't that many drastic changes from 2007.