利用SmtpClient类发送邮件

以qq邮箱为例

1.首先去配置smtp服务(QQ邮箱默认的SMTP服务是关闭的，要自己去开)

首先打开QQ邮箱界面，点击设置》账户

2.代码配置部分

public ActionResult SendMali() {
            try
            {
                string _from = "发件人地址";
                string to = "收件人地址";
                string password = "**********";//授权码
                SmtpClient mailClient = new SmtpClient("smtp.qq.com");
                //设置邮箱端口，pop3端口:110, smtp端口是:25 
                mailClient.Port = 25;
                mailClient.EnableSsl = true;
                mailClient.UseDefaultCredentials = false;
                //Credentials登陆SMTP服务器的身份验证.
                mailClient.Credentials = new NetworkCredential(_from, password);
                //test@qq.com发件人地址、test@tom.com收件人地址
                MailMessage message = new MailMessage(new MailAddress(_from), new MailAddress(to));
                message.Body = "this is a Body!";//邮件内容
                message.Subject = "this is a Subject";//邮件主题
                string path = Server.MapPath("/upload/demo.rar");
                Attachment a = new Attachment(path);//附件
                message.Attachments.Add(a);
                mailClient.Send(message);
                return Json("发送成功");
            }
            catch (Exception)
            {

                return Json("发送失败");
            }
        }

3.SmtpClient类官方api  https://msdn.microsoft.com/zh-cn/library/system.net.mail.smtpclient(v=vs.110).aspx