使用OAuth2.0连接Outlook时抛出“基础连接已关闭”错误求助

我参考微软官方示例编写了一段C#代码，通过OAuth2.0连接Outlook，但运行时抛出异常：The underlying connection was closed: An unexpected error occurred on a send.

代码片段如下：

// Using Microsoft.Identity.Client 4.22.0
var cca = ConfidentialClientApplicationBuilder
    .Create(System.Configuration.ConfigurationManager.AppSettings["appId"])
    .WithClientSecret(System.Configuration.ConfigurationManager.AppSettings["clientSecret"])
    .WithTenantId(System.Configuration.ConfigurationManager.AppSettings["tenantId"])
    .Build();

var ewsScopes = new string[] { "https://outlook.office365.com/.default" };

try
{
    var authResult = await cca.AcquireTokenForClient(ewsScopes)
        .ExecuteAsync();

    // Configure the ExchangeService with the access token
    var ewsClient = new ExchangeService();
    ewsClient.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");
    ewsClient.Credentials = new OAuthCredentials(authResult.AccessToken);
    ewsClient.ImpersonatedUserId =
        new ImpersonatedUserId(ConnectingIdType.SmtpAddress, "capmodauthtesting@test.com");

    //Include x-anchormailbox header
    ewsClient.HttpHeaders.Add("X-AnchorMailbox", "capmodauthtesting@test.com");

    // Make an EWS call
    var folders = ewsClient.FindFolders(WellKnownFolderName.MsgFolderRoot, new FolderView(10));
    foreach(var folder in folders)
    {
        Console.WriteLine("Folder: {folder.DisplayName}");
    }
}
catch (MsalException ex)
{
    Console.WriteLine("Error acquiring access token: {ex}");
}
catch (Exception  ex)
{
    //Console.WriteLine("Error: {ex}");
    MessageBox.Show(ex.InnerException.Message);
}

if (System.Diagnostics.Debugger.IsAttached)
{
    Console.WriteLine("Hit any key to exit...");
    Console.ReadKey();
}

该代码来源于微软官方文档，请求协助排查该异常原因。

内容的提问来源于stack exchange，提问作者niran kumar