Outlook on the web mailbox policies in Exchange Online
In Exchange Online, Outlook on the web mailbox policies control the availability of settings and features in Outlook on the web (formerly known as Outlook Web App). A mailbox can only have one Outlook on the web mailbox policy applied to it. You can create different policies for different types of users in your Exchange Online organization.
Every Exchange Online organization has a default Outlook on the web mailbox policy named OwaMailboxPolicy-Default that's applied to all user mailboxes. You can use this policy or create additional policies as necessary to meet the needs of your organization.
For the procedures that you can do on Outlook on the web mailbox policies, see Outlook on the web mailbox policy procedures in Exchange Online.