MailMessage+SmtpClient 发送邮件

private static void SendMail(string to, string from,string content)        {            string subject="Mail Title";//邮件标题            string strSmtpServer= "smtp.163.com";//服务器            string strSmtpUserName = "登录账号@163.com";//登录用户            string strSmtpUserPwd = "登录密码";//登录密码            if (string.IsNullOrEmpty(to)) return;            MailMessage mail = new MailMessage(from, to, subject, content); //创建邮件信息            if (File.Exists("D:/login.png"))            {                Attachment attach=new Attachment("D:/login.png"); //添加附件                //FileStream file = new FileStream("D:/login.png", FileMode.Open);                //Attachment attachStream = new Attachment(file, "login.png"); //通过文件流添加附件                mail.Attachments.Add(attach);            }            SmtpClient client = new SmtpClient(strSmtpServer); //创建SMTP客户端            try            {                client.Credentials = new System.Net.NetworkCredential(strSmtpUserName, strSmtpUserPwd);//登录客户端                 client.Send(mail);//发送邮件  邮件发送方必须和登录用户一致            }            catch (Exception)            {                            }        }