C# SmtpClient 发邮件

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Mail;
using System.Net; 
using System.Threading;
using System.IO;
using System.Security.Cryptography;

namespace ConsoleApp348
{
    class Program
    {        
        static string logFullPath = Directory.GetCurrentDirectory() + "\\" + DateTime.Now.ToString("yyyyMMdd") + ".txt";
        static void Main(string[] args)
        {
            Timer emailTimer = new Timer(SendMailCallBack, null, 0, 1);
            Console.ReadLine();
        }

        private static void SendMailCallBack(object state)
        {
            string fromMail = "fromMail";
            string fromMailPwd = "fromMailPwd";
            string toMail = "toMail";
            MailExample(fromMail, fromMailPwd, toMail);
        }

        static void MailExample(string fromEmail, string fromEmailPwd, string toEmail)
        {            
            try
            {
                using (SmtpClient smtpClient = new SmtpClient())
                {
                    smtpClient.Host = "smtp.163.com";
                    smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
                    smtpClient.UseDefaultCredentials = false;
                    smtpClient.Credentials = new System.Net.NetworkCredential(fromEmail, fromEmailPwd);
                    using (MailMessage mail = new MailMessage())
                    {
                        mail.BodyEncoding = UTF8Encoding.UTF8;
                        mail.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;
                        mail.From = new MailAddress(fromEmail);
                        mail.To.Add(new MailAddress(toEmail));
                        mail.Subject = $"This is the new test.Now is {DateTime.Now.ToString("mmssffff")}";
                        mail.Body = $"This is the mail body,And now is {DateTime.Now.ToString("yyyyMMddHHmmssffff")}";
                        smtpClient.SendAsync(mail, $"Frommail:{fromEmail},ToMail:{toEmail},send email successfully!");
                        smtpClient.SendCompleted += SmtpClient_SendCompleted;
                    }                        
                }                    
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.StackTrace);
                LogMessage(ex.StackTrace);
            }
        }

        private static void SmtpClient_SendCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
        {
            Console.WriteLine(e.UserState);
            LogMessage(e.UserState.ToString());
        }

        static void LogMessage(string msg)
        {            
            lock(logFullPath)
            {
                using (StreamWriter logWriterStream = new StreamWriter(logFullPath, true, UTF8Encoding.UTF8))
                {
                    logWriterStream.WriteLine($"Log message :{msg},now is {DateTime.Now.ToString("yyyyMMddHHmmssffff")}");
                }
            }           
        }
    }
}