Add project files.

Program.cs

@@ -0,0 +1,25 @@
+namespace OutlookEmailListener;
+
+using Outlook = Microsoft.Office.Interop.Outlook;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Outlook.Application outlookApp = new Outlook.Application();
+        Outlook.MAPIFolder inbox = outlookApp.Session.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderInbox);
+        Outlook.Items items = inbox.Items;
+        items.ItemAdd += new Outlook.ItemsEvents_ItemAddEventHandler(OnNewMail);
+
+        Console.WriteLine("Press any key to exit...");
+        Console.ReadKey();
+    }
+
+    private static void OnNewMail(object item)
+    {
+        if (item is Outlook.MailItem mail)
+        {
+            Console.WriteLine("New mail received: {0}", mail.Subject);
+        }
+    }
+}