Mail send class, support HTML format, support priority setting. Implemented through the socket class. The problem has finally been solved.

Using System;
Using System.Text;
Using System.IO;
Using System.Net;
Using System.Net.Sockets;
Namespace Blood.Com.ClassLib
{
<summary>
TcpClient derived class for connecting to the SMTP server
</summary>
public class Smtpclient:tcpclient
{
public bool IsConnected ()
{
return Active;
}
public void Sendcommandtoserver (string Command)
{
NetworkStream ns = this. GetStream ();
Byte[] WriteBuffer;
WriteBuffer = new byte[1024];
WriteBuffer = Encoding.Default.GetBytes (Command);
Ns. Write (writebuffer,0,writebuffer.length);
return;
}
public string Getserverresponse ()
{