I've had 3 Outlook 2016 users contact me today with the same problem.
When they click any email, in there inbox, the preview pane is blank (as shown below):
Also, if they double-click any email (to open it in a new window) that email body is also blank.
I've tried updating Microsoft Office 2016 and the problem persisted after being fully updated.
Additionally, I tried deleting a user's email profile, and then re-syncing their email using Google App Sync (because the server is not exchange; it is Gmail). Even after a fresh re-sync the problem persists. Of course, if these users check their Gmail, the email bodies show just fine.
Have any of you experienced this issue, and if so, how did you get past it?