How can I send push notifications to an outlook add-in from a web server?

Question

Problem

I can't seem to find a reference a suggested way to implement sending notifications from a web server to an outlook add-in.

I've looked on:

• the officeJS docs, which have a deprecated entry about notifications rest api v2.0, pointing to the Microsoft Graph, which again is deprecated (but without pointing to any up to date version)
• stackoverflow, but the questions were either unanswered, or, answering the question with the deprecated notifications api
• the officejs Q&A forum, where someone pointed out the Azure Notifications Hub service, but only linked to an android example; but the docs state that it's primarily made to send messages to mobile devices officejs add-ins as a tutorial or reference

Could you help me understand what's the best way to implement push notifications from web server -> outlook add-in?

Context

• I personally would like to use Firebase Cloud Messaging, which depends on the Push API under the hood. Is the Push API supported?
• WebSockets could also work, but here again I wasn't able to find something before working away on an implementation

Answer 1

@nickromano is correct in that an add-in is just a webpage embedded in Outlook, so you may be able to send data to it through websockets or long polling outside of a standard request. However, this is not a supported use case scenario.