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;
            }
        }

     
    }
}