Options > Outlook Web App version
support.microsoft.com › en-us › officeThe light version of Outlook Web App is designed for use with older web browsers that aren't supported by the standard version of Outlook Web App, for use over slow connections, and to meet accessibility needs by providing a simplified interface that’s easier to use with screen readers.
Outlook Web App > Options
support.microsoft.com › en-us › officeYou can customize Outlook Web App using the settings available in the following options: Options > Regional Settings Options > Messaging Options > Junk Email Options > Calendar Options > Automatic Replies Options > Change Password Options > Outlook Web App version Options > Mobile Devices Options > About