Subscribe to Outlook/Office 365 API Status Code NotFound in C#

Question

I am getting an issue when creating subscription. My steps are:

1. Register app at https://apps.dev.microsoft.com
2. Update permissions Read Mail and User's info
3. Then update code, do same steps at https://learn.microsoft.com/en-us/outlook/rest/dotnet-tutorial

4. After login, I can get access token Screen after login

5. Then I try to create a subscription for Inbox

   var newSub = new Subscription
   {
       Resource = "me/mailFolders{'Inbox'}/messages",
       ChangeType = "created,updated",
       NotificationUrl = notificationUrl,
       ClientState = clientState,
       ExpirationDateTime = DateTime.Now.AddMinutes(15)
   };
   var result = await graphClient.Subscriptions.Request().AddAsync(newSub);
   

6. Implement for notification in notification URL - I can get validation token and return in plain text.

   public async Task<ActionResult> Listen()
   {
       if (Request.QueryString["validationToken"] != null)
       {
           var token = Request.QueryString["validationToken"];
           return Content(token, "plain/text");
       }
   }
   

7. But I always get this error.

Is there anyone know problem?

Answer 1

You must expose a public HTTPS endpoint to create a subscription and receive notifications from Microsoft Graph.