A dark theme, that is as dark as the Visual Studio (dark) Theme
Yes, a dark viewing option for the content pane(s) would be helpful for night viewing
Please save our eyes and give us a dark themes for all apps in the Office 365 online suite. I don't need to stare at a mostly white screen all day. Other Microsoft applications like Visual Studio have dark themes (dark background) including Windows! It's so much kinder on the eyes and so much more energy efficient to have dark backgrounds.
samuel bonnallie commented
Dark theme everywhere...
A dark theme as VS 2017, but with a bit more contrasting colors.
Another point is that with the dark grey mode on Outlook, it is very "difficult" to spot how many new e-mails there exists - the same color as the legend (Inbox 3).
Same request for Office 2016 for Mac.