How to read User's email message from Extermal Azure AD using Graph SDK in C#

Question

class Program
{
static void Main(string[] args)
{
ReadEmail();
}
public static async void ReadEmail()
{
var scopes = new[] { "https://graph.microsoft.com/v1.0/dashmagiq@vidyatech.in/mailFolders/Inbox/messages?$filter=isRead" };
var tenantId = ConfigurationManager.AppSettings["tenantId"];
var appId = ConfigurationManager.AppSettings["appId"];
var clientSecret = ConfigurationManager.AppSettings["clientSecret"];
var clientSecretCredential = new ClientSecretCredential(
tenantId, appId, clientSecret);
GraphServiceClient graphClient = new GraphServiceClient(clientSecretCredential, scopes);
//var inboxMessages = graphClient
// .Users["dashmagiq@vidyatech.in"]
// .MailFolders["inbox"]
// .Messages
// .Request()
// .Expand("attachments")
// .Top(20)
// .GetAsync();
var inboxMessages = await graphClient.Me
//./Users["dashmagiq@vidyatech.in"]/
.MailFolders["inbox"]
.Messages
.Request()
.GetAsync();

Answer 1

The value for the variable scopes is wrong. You need to set this to the Microsoft Graph permission scopes necessary to read email messages from all mailboxes. Because you're using application permissions, this permission request should be made in the Azure Portal rather in your code.

First, request the Mail.Read application permission.

Then grant that permission.

Then set the value of scopes as shown below. This tells Microsoft Graph to use the permissions configured in the Azure Portal.

var scopes = new[] { "https://graph.microsoft.com/.default" };

Here are links to a couple Microsoft Learn training paths that can give you some more foundational training on how to use Microsoft Graph.

Microsoft Graph Fundamentals

MS-600: Build apps with Microsoft Graph - Associate