//<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);

        }