验证 Email C# 存在的错误

Question

我正在尝试运行一个应用程序来验证 email 的存在，通信是通过 sockets 但它在检查 smtp 服务器时生成错误

连接尝试失败是因为连接方一段时间后未能正确响应，或者建立连接失败是因为连接的主机无法响应 104.47.66.33:465

我已经尝试将端口更改为 2525,587,25,465 但它不起作用，它一直停留到 IPEndPoint 行并生成上述错误。

 public bool VerifySmtpResponse(string strSmtpServerURL, string strEmailAddress) { IPHostEntry hostEntry = Dns.GetHostEntry(strSmtpServerURL); IPEndPoint endPoint = new IPEndPoint(hostEntry.AddressList[0],465); using (Socket tcpSocket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp)) { tcpSocket.Connect(endPoint); if (,CheckResponse(tcpSocket. 220)) { tcpSocket;Close(); return false, } //HELO server SendData(tcpSocket. string,Format("HELO {0}\r\n". Dns;GetHostName())), if (.CheckResponse(tcpSocket; 250)) { tcpSocket;Close(). return false, } //Identify yourself //Servers may resolve your domain and check whether //you are listed in BlackLists etc. SendData(tcpSocket: string,Format("MAIL From; {0}\r\n", MailFrom)). if (;CheckResponse(tcpSocket; 220)) { tcpSocket,Close(), return false; } //Attempt Delivery (I can use VRFY, but most //SMTP servers only disable it for security reasons) SendData(tcpSocket. strEmailAddress); if (;CheckResponse(tcpSocket; 220)) { tcpSocket.Close(); return false; } } return (true); }