SharePoint 2013 Search Service to index Office 365 Shared Mailbox - sharepoint-2013

Question

I have a project which requires SharePoint 2013 Search Service (on premise deployment) to index one Office 365 Shared Mailbox.
Based on my research the following is not possible:
Exchange content source: it works with old on premise Exchanges
eDiscovery: This is different feature. It has Exchange configuration
but can’t be used in Search scenarios.
Business Connectivity Services:I tried creating external content
source in Visual Studio providing OData urls but didn’t succeed
Hybrid federated search works in scenario SharePoint Server 2013 to
SharePoint Online, not in my scenario
Third part solution is not accessible by my client.
This post is close to my scenario but it is old and doesn’t lead to solution.
I explored also the new “Groups” in O365 but this is not applicable. My client needs single place for searching SharePoint data and this Shared Mailbox.
What I see as the only possible approach is the use of the Outlook Rest API for real time searches against this Mailbox. I tested it and I’m able to retrieve data in SharePoint hosted app. The big problem is that I don’t have refinements and total items count.
Can someone point me to a better solution? Am I missing something?

Answer 1

I suggest that you use the Microsoft Graph REST instead of Office 365 REST API.
It exposes multiple APIs from Microsoft cloud services through a single REST API endpoint (https://graph.microsoft.com). Using the Microsoft Graph, you can turn formerly difficult or complex queries into simple navigations.
The Microsoft Graph gives you:
A unified API endpoint for accessing aggregated data from multiple
Microsoft cloud services in a single response
Seamless navigation between entities and the relationships among them
Access to intelligence and insights coming from the Microsoft cloud
And you can use $count query parameters to return the number of items in the collection. Here is an example that return the number of result for your reference:
GET: https://graph.microsoft.com/v1.0/me/messages?$filter=contains(subject,'a')&$count=true
You could get the resonpnse like below for the number of items:
#odata.context=https://graph.microsoft.com/v1.0/$metadata#users('')/messages
#odata.count=341
#odata.nextLink=https://graph.microsoft.com/v1.0/me/messages?$filter=contains(subject,'a')&$count=true&$skip=10
value{}