Use the notifications REST API in Microsoft Graph
Important: APIs under the /beta version in Microsoft Graph are in preview and are subject to change. Use of these APIs in production applications is not supported.
You can use the notifications API in Microsoft Graph to send push notifications to a user. Simply target a user account to send a notification to, and the platform will deliver the notification to all device endpoints. Notifications API requests are performed on behalf of a user via delegated permissions and the notification permission, which can be used with either Microsoft accounts or work or school accounts. This type of user-centric notification is represented by the notification resource and is stored in Microsoft Graph. It can then be accessed and managed by the publishing app via the Project Rome SDK APIs.