MailMessage mail = new MailMessage();
mail.From = new MailAddress("发送者", "名字");
mail.To.Add(new MailAddress("接收者", "名字"));
mail.Subject = "标题";
mail.Body = "内容";
SmtpClient smtp = new SmtpClient("smtp.qq.com");//服务器
smtp.Credentials = new NetworkCredential("用户名", "密码");
smtp.Send(mail);