Outlook 2016 for Mac & RTF/TNEF
This is really just to bitch at Microsoft - I had a customer yesterday who complained she frequently received e-mails from different people with the classic winmail.dat issue. She also stated she wanted excel/word/etc. So my solution was to install Office Home & Business for Mac because it would solve all those issues.
Turns out Outlook for Mac can't read TNEF/RTF regardless of what this support article says:
"...All versions of Microsoft Outlook fully understand TNEF..."
Argh. What a way to waste a few hours in a day.