Microsoft has been introducing a dark mode for its Office apps for over a year. This change has been available for several months in Outlook for the desktop and the web and is now available for Android, iPhone and iPad. To enable the topic:
The instructions for enabling Outlook's dark mode are the same for all mobile devices. If the topic option does not appear, look for an app update. The dark mode should be available for Android 4.0.4 (345) and higher. iPhone and iPad owners should have Outlook version 4.2.0 or higher installed.
Launch the Outlook app on your Android, iPhone or iPad. Then tap the gear icon in the lower-left corner of the interface.
Scroll down the Settings menu to the "Settings" section and then select the "Theme" option.
. Change the topic option from "Bright" to "Dark".
The moment you select "Dark," the Outlook app inverts the white background in black and the black text in white.
Alternately: a The third option labeled "Set by Battery Saver" is automatically activated when your mobile device enters Battery Saver mode. Dark mode does not necessarily increase battery life, but it does not hurt.
Note: For users with limited accessibility, dark mode is not optimized for high-contrast modes. Some elements, eg. Images and highlights are not converted, so they may not look good.
Also, the message body at the time of writing remains white when you edit a draft. Microsoft is working on adding a dark mode to the editor, but it may take some time to fully implement the design.