该帐户没有冒充所请求用户的权限

在尝试访问资源邮箱时出现此错误。请在这个问题上帮助我。我是EWS的新手。

我可以通过OWA(Outlook web app)访问资源邮箱。但是我不是这个邮箱的所有者，因为它是共享邮箱。

我代码:

ServicePointManager.ServerCertificateValidationCallback = CertificateValidationCallBack;
ExchangeService newExchangeService = new ExchangeService  (ExchangeVersion.Exchange2007_SP1);
newExchangeService.Credentials = new NetworkCredential(username, password, domain);
newExchangeService.AutodiscoverUrl(email-id, RedirectionUrlValidationCallback);
newExchangeService.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, email_which_i_want_to_access);
Folder visitorsFolder = Folder.Bind(newExchangeService, WellKnownFolderName.Inbox);
foreach (Folder childfolder in visitorsFolder.FindFolders(new FolderView(10)))
        {
            Console.WriteLine(childfolder.DisplayName);
        }