string fromAddress = "***@gmail.com";

            System.Net.Mail.MailMessage msg = new System.Net.Mail.MailMessage();
            msg.To.Add(targetAddress);
            msg.From = new System.Net.Mail.MailAddress(fromAddress,"***");
            msg.BodyEncoding = System.Text.Encoding.UTF8;
            /* 上面3个参数分别是发件人地址（可以随便写），发件人姓名，编码*/
            msg.Subject = title;//邮件标题 
            msg.SubjectEncoding = System.Text.Encoding.UTF8;//邮件标题编码 
            msg.Body = content;//邮件内容 
            msg.BodyEncoding = System.Text.Encoding.UTF8;//邮件内容编码 
            msg.IsBodyHtml = true;//是否是HTML邮件 
            msg.Priority = System.Net.Mail.MailPriority.High;//邮件优先级 
            System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient();
            client.Credentials = new System.Net.NetworkCredential(fromAddress, "***");
            //上述写你的GMail邮箱和密码 
            client.Port = 587;//Gmail使用的端口 
            client.Host = "smtp.gmail.com";
            client.EnableSsl = true;//经过ssl加密 
            object userState = msg;
            client.SendAsync(msg, userState);