Outlook on the web in Exchange Online
By default, Outlook on the web (formerly known as Outlook Web App) is enabled in Exchange Online, and lets users access their mailbox from almost any web browser.
For information about client access mailbox methods in Exchange Online, see Clients and mobile in Exchange Online.
Overview of Outlook on the web
Fully supported web browsers give users access to features such as conversation view, Inbox rules, the reading pane, and the Scheduling Assistant. Browsers that aren't fully supported can still be used, but users will see the light version of Outlook on the web, which has fewer features.
Managing Outlook on the web
In Exchange Online, the most common Outlook on the web management tasks can be accomplished in the Exchange admin center (EAC). All these tasks, and many others, can be accomplished by using Exchange Online PowerShell.