邮件发送类，支持HTML格式，支持优先级设置。通过SOCKET类实现的
using System;
using System.Text;
using System.IO;
using System.Net;
using System.Net.Sockets;

namespace Blood.Com.ClassLib
{
/// <summary>
/// TcpClient派生类，用来进行SMTP服务器的连接工作
/// </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()
{
int StreamSize ;
string ReturnValue = "" ;
byte[] ReadBuffer ;
NetworkStream ns = this.GetStream() ;
ReadBuffer = new byte[1024] ;
StreamSize = ns.Read(ReadBuffer,0,ReadBuffer.Length);
if (StreamSize==0)
{
return ReturnValue ;
}
else
{
ReturnValue = Encoding.Default.GetString(ReadBuffer);
return ReturnValue;
}
}

public bool DoesStringContainSMTPCode(string s,string SMTPCode)
{
return(s.IndexOf(SMTPCode,0,10)==-1)?false:true;
}

} //结束类

/// <summary>
/// 发送邮件类
/// </summary>
public class SMTPMail
{
/// <summary>
/// 错误反馈信息
/// </summary>
private string strErrMessage = null;

/// <summary>
/// SMTP服务器反馈的信息
/// </summary>
private string strResponse;

/// <summary>
/// 构造函数
/// </summary>
public SMTPMail()
{
strErrMessage = "";
strResponse = "";
}

/// <summary>
/// 取得错误反馈信息
/// </summary>
public string ErrorMessage
{
get
{
return strErrMessage ;
}
}

/// <summary>
/// 取得SMTP服务器反馈的信息
/// </summary>
public string ServerResponse
{
get
{
return strResponse;
}
}

/// <summary>
/// 邮件发送优先级
/// </summary>
public enum Prioritys
{
/// <summary>
/// 最高级别
/// </summary>
HIGH = 1,
/// <summary>
/// 默认级别
/// </summary>
NORMAL = 3,
/// <summary>
/// 最低级别
/// </summary>
LOW = 5
}

public void SendMail(string SmtpHost,int Port,string From,string DisplayFromName,string To,string DisplayToName,Prioritys Priority,bool HTML,string Base,string Subject,string Message)
{
try
{
string strResponseNumber;
SMTPClient smtpcMail = new SMTPClient();
smtpcMail.Connect(SmtpHost,Port);