Is Office.context.mailbox.item.getSharedPropertiesAsync() to be deprecated in 2022?

Question

My Outlook add-in imports emails into a database and I am migrating it from using the Outlook REST API to Microsoft Graph as per this notice:
https://developer.microsoft.com/en-us/graph/blogs/outlook-rest-api-v2-0-deprecation-notice/

For an email in a shared mailbox, the add-in currently calls getSharedPropertiesAsync() on the client-side to retrieve the targetMailbox, that is then sent to the server-side to retrieve the shared Message with:
message = await graphClient.Users[targetMailbox].Messages[messageId].Request().GetAsync();

I'm aware that in order to call getSharedPropertiesAsync(), you must first retrieve a REST access token using:
mailbox.getCallbackTokenAsync({ isRest: true }

Therefore, is getSharedPropertiesAsync() part of the REST API that is to be deprecated in 2022?
Is there an alternative way to access an email Message (using a Message ID) in a shared mailbox using only the Graph in server-side code?

Answer 1

Answering the Graph API bit of the question.

With Graph API, for a shared mailbox, you can access the message using the message-id and the user-id of the owner of the mails using Get Message.
When using delegated permissions you will need Mail.Read.Shared permission added to your app. See this thread for more.

GET https://graph.microsoft.com/v1.0/users/shared@contoso.com/messages  
  
{  
    "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users('shared%40contoso.com')/messages(id)",  
    "value": [  
        {  
            "@odata.etag": "W/\"CQAAA...\"",  
            "id": "AQMk...AIf-wAAAA=="  
        },  
        {  
            "@odata.etag": "W/\"CQAAABYA...\"",  
            "id": "AQM...AAAIJPwAAAA=="  
        }  
    ]  
}