简单的客户端邮件发送系统（winform版） .

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net.Mail;
using System.Net;

namespace _13._1._4练习
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
MailMessage msg = new MailMessage();

msg.Subject = this.textBox2.Text; //标题
msg.Body = this.textBox3.Text; //内容
msg.From=new MailAddress("duan_linlin@163.com"); //邮件来自哪
msg.To.Add(this.textBox1.Text);
SmtpClient client=new SmtpClient(); //允许传输协议
client.Host = "smtp.163.com"; //发件方服务器地址
client.Port = 25; //发件方端口
NetworkCredential credential = new NetworkCredential();
credential.UserName = "duan_linlin@163.com";
credential.Password = "jinyuxueqi521";
client.Credentials = credential; //说明证书要给代理证书credential

Attachment att = new Attachment(this.textBox4.Text);
msg.Attachments.Add(att);

client.Send(msg);
}

private void Form1_Load(object sender, EventArgs e)
{

}

private void button2_Click(object sender, EventArgs e)
{
if (this.openFileDialog1.ShowDialog()==System.Windows.Forms.DialogResult.OK)
{
this.textBox4.Text = this.openFileDialog1.FileName;
}
}

}
}