C# 检查SSL证书到期日期并在指定的计划时间自动发送邮件的Windows服务

我是新手，我正在编写一个代码，该代码将检查SSL证书的到期日期，并定期或按计划时间向受尊敬的用户发送邮件。在配置设置中，我将间隔设置为一分钟，并将代码设置为在名为SSLLog.txt的文本文件中写入某些事件。我能够以本地用户的身份运行它，并且它作为服务成功运行，但它不会向受尊敬的用户发送邮件。请帮忙。下面是Service1.cs的代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;
using System.IO;
using System.Threading;
using System.Configuration;
using System.Security.Cryptography.X509Certificates;
using System.Net;
using System.Security;

namespace WindowsServiceCS
{
    public partial class Service1 : ServiceBase
    {
        public Service1()
        {
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
        {
            this.WriteToFile("Simple Service started {0}");
            this.ScheduleService();
        }

        protected override void OnStop()
        {
            this.WriteToFile("Simple Service stopped {0}");
            this.Schedular.Dispose();
        }

        private Timer Schedular;

        public void ScheduleService()
        {
            try
            {
                Schedular = new Timer(new TimerCallback(SchedularCallback));
                string mode = ConfigurationManager.AppSettings["Mode"].ToUpper();
                this.WriteToFile("Simple Service Mode: " + mode + " {0}");

                //Set the Default Time.
                DateTime scheduledTime = DateTime.MinValue;

                if (mode == "DAILY")
                {
                    //Get the Scheduled Time from AppSettings.
                    scheduledTime = DateTime.Parse(System.Configuration.ConfigurationManager.AppSettings["ScheduledTime"]);
                    if (DateTime.Now > scheduledTime)
                    {
                        //If Scheduled Time is passed set Schedule for the next day.
                        scheduledTime = scheduledTime.AddDays(1);
                    }
                }

                if (mode.ToUpper() == "INTERVAL")
                {
                    //Get the Interval in Minutes from AppSettings.
                    int intervalMinutes = Convert.ToInt32(ConfigurationManager.AppSettings["IntervalMinutes"]);

                    //Set the Scheduled Time by adding the Interval to Current Time.
                    scheduledTime = DateTime.Now.AddMinutes(intervalMinutes);
                    if (DateTime.Now > scheduledTime)
                    {
                        //If Scheduled Time is passed set Schedule for the next Interval.
                        scheduledTime = scheduledTime.AddMinutes(intervalMinutes);
                    }
                }

                TimeSpan timeSpan = scheduledTime.Subtract(DateTime.Now);
                string schedule = string.Format("{0} day(s) {1} hour(s) {2} minute(s) {3} seconds(s)", timeSpan.Days, timeSpan.Hours, timeSpan.Minutes, timeSpan.Seconds);

                this.WriteToFile("Simple Service scheduled to run after: " + schedule + " {0}");

                //Get the difference in Minutes between the Scheduled and Current Time.
                int dueTime = Convert.ToInt32(timeSpan.TotalMilliseconds);

                //Change the Timer's Due Time.
                Schedular.Change(dueTime, Timeout.Infinite);
            }
            catch (Exception ex)
            {
                WriteToFile("Simple Service Error on: {0} " + ex.Message + ex.StackTrace);

                //Stop the Windows Service.
                using (System.ServiceProcess.ServiceController serviceController = new System.ServiceProcess.ServiceController("SimpleService"))
                {
                    serviceController.Stop();
                }
            }
        }

        private void SchedularCallback(object e)
        {
            try
            {
                ServicePointManager.ServerCertificateValidationCallback += ServerCertificateValidationCallback;

                var request = WebRequest.Create("https://www.google.co.in");

                var response = request.GetResponse();
                WriteToFile("Check Completed");
            }
            catch(Exception ex)
            {
                WriteToFile("The Exception caused is " + ex);
            }
            this.WriteToFile("Simple Service Log: {0}");
            this.ScheduleService();
        }
        private bool ServerCertificateValidationCallback(object sender, X509Certificate certificate, X509Chain chain, System.Net.Security.SslPolicyErrors sslPolicyErrors)
        {
            try
            {
                WriteToFile("Certificate expires on " + certificate.GetExpirationDateString());
                string name = "Tillapudi Venkata Sundeep";
                string email = "xxxxxxxx1@gmail.com";
                WriteToFile("Trying to send email to: " + name + " " + email);
                System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient();
                client.Port = 587;
                client.Host = "smtp.gmail.com";
                client.EnableSsl = true;
                client.Timeout = 10000;
                client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
                client.UseDefaultCredentials = true;
                client.Credentials = new System.Net.NetworkCredential("xxxxxxxx@gmail.com", "xxxxxxxxx");
                System.Net.Mail.MailMessage mm = new System.Net.Mail.MailMessage("xxxxxxxx@gmail.com", "xxxxxxxx1@gmail.com", "Test Mail Sent From Visual Studio", "Hey buddy How are you doing");
                mm.BodyEncoding = System.Text.UTF8Encoding.UTF8;
                mm.DeliveryNotificationOptions = System.Net.Mail.DeliveryNotificationOptions.OnFailure;
                WriteToFile("Mail Sent");
                client.Send(mm);
                WriteToFile("Mail Sent");
            }
           catch(Exception exce)
            {
                WriteToFile("The Execption caused in the mail" +exce);
            }
            return true;
        }


        private void WriteToFile(string text)
        {
            string path = "C:\\SSlLog.txt";
            using (StreamWriter writer = new StreamWriter(path, true))
            {
                writer.WriteLine(string.Format(text, DateTime.Now.ToString("dd/MM/yyyy hh:mm:ss tt")));
                writer.Close();
            }
        }
    }
}