The Security & privacy settings

This is the page you use to set your Office 365 Password policy (options include the days before passwords expire and the number of days before a user is notified of imminent password expiration), the Sharing settings (whether your users can add guest users—with this setting off, users cannot share with external users from OneDrive or SharePoint), and self-service password reset:

The Security & privacy settings

If your company has the Customer Lockbox feature, this is also where you can turn it on or off.