//<发送>按钮
        private void button1_Click(object sender, EventArgs e)
        {
            //设置要调用的发送邮件的服务器
            SmtpClient smtp = new SmtpClient("smtp.qq.com");
            //创建发件人对象
            MailAddress from = new MailAddress(textBox1.Text);
            //创建收件人对象
            MailAddress to = new MailAddress(textBox2.Text);
            //要发送的邮件对象，包含四个内容要填充
            MailMessage mail = new MailMessage(from,to);
            //设置邮件的标题
            mail.Subject = textBox3.Text;
            //设置邮件的主题正文格式
            mail.Body = textBox4.Text;
            //创建发件人身份验证凭证
            NetworkCredential cred = new NetworkCredential(textBox1.Text,textBox5.Text);
            //将凭证证书绑定到服务端对象上，一并发送出去
            smtp.Credentials = cred;
            //此服务器对象执行发送邮件功能
            smtp.Send(mail);
        }