原始碼：
using System;
using System.Windows.Forms;

using System.Net.Mail;
using System.Text.RegularExpressions;

namespace 郵件
{
public partial class Form1 : Form
{
string fileName;//獲取檔名
public Form1()
{
InitializeComponent();
}

    private void button傳送_Click(object sender, EventArgs e)
    {
        SmtpClient client = new SmtpClient();//生成SmtpClient例項，用它傳送電子郵件
        client.Host = "smtp.163.com";//指定SMTP伺服器主機
        client.Port = 25;//指定要使用的埠
        client.Credentials = new System.Net.NetworkCredential("
 
[email protected]", "xxxxxx");//驗證使用者名稱和密碼
        MailMessage message = new MailMessage();
        MailAddress from = new MailAddress(txtSender.Text);//獲取輸入的發件人郵箱地址
        if (txtReceiver.Text != "")
        {
            if (Regex.IsMatch(txtReceiver.Text, "\\[email protected]\\w+(\\.\\w+)+"))  //用正則表示式驗證郵箱
            {
                MailAddress to = new MailAddress(txtReceiver.Text);//獲取輸入的收件人郵箱地址
                message.To.Add(to);//設定郵件接收人，MailMessage類的To屬性可以Add多個接收人
            }
            else
            {
                MessageBox.Show("收件人郵箱地址不正確");
                return;
            }
        }
        else
        {
            MessageBox.Show("收件人不能為空");
            return;
        }
        if (txtCc.Text != "")
        {
            if (Regex.IsMatch(txtCc.Text, "\\
 
[email protected]\\w+(\\.\\w+)+"))
            {
                MailAddress cc = new MailAddress(txtCc.Text);//獲取輸入的抄送人郵箱地址
                message.CC.Add(cc);//設定郵件抄送人，MailMessage類的To屬性可以Add多個抄送人
            }
            else
            {
                MessageBox.Show("抄送人郵箱地址不正確");
                return;
            }
        }

        if (txtAttachFileName.Text != "")
        {
            fileName = txtAttachFileName.Text;//獲取檔名
            Attachment attach = new Attachment(fileName);//獲取選擇的附件
            message.Attachments.Add(attach);//將附件新增到郵件中，MailMessage類的Attachments屬性可以Add多個附件          
        }
        message.Subject = txtTitle.Text;//獲取輸入的郵件標題
        message.Body = rtbContext.Text;//獲取輸入的郵件正文
        message.From = from;//設定郵件發件人          
        client.Send(message);
        MessageBox.Show("傳送成功");
    }

    private void button新增附件_Click(object sender, EventArgs e)
    {
        OpenFileDialog ofd = new OpenFileDialog();
        ofd.Filter = "所有檔案(*.*)|*.*";
        if (ofd.ShowDialog() == DialogResult.OK)
        {
            txtAttachFileName.Text = ofd.FileName;
        }
    }
}
 

}