检查电子邮件状态或收件人状态c#

using System;
using System.Net;
using System.Net.Mail;

class Program
{
    static void Main(string[] args)
    {
        // 设置SMTP服务器信息
        SmtpClient smtpClient = new SmtpClient("smtp.example.com", 587);
        smtpClient.EnableSsl = true;
        smtpClient.Credentials = new NetworkCredential("your_username", "your_password");

        // 创建邮件对象
        MailMessage mailMessage = new MailMessage();
        mailMessage.From = new MailAddress("sender@example.com");
        mailMessage.To.Add("recipient@example.com");
        mailMessage.Subject = "Hello";
        mailMessage.Body = "This is a test email.";

        // 发送邮件
        smtpClient.SendCompleted += SmtpClient_SendCompleted;
        smtpClient.SendAsync(mailMessage, null);

        Console.ReadLine();
    }

    private static void SmtpClient_SendCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
    {
        if (e.Cancelled)
        {
            Console.WriteLine("Email sending cancelled.");
        }
        else if (e.Error != null)
        {
            Console.WriteLine("Email sending failed: " + e.Error.Message);
        }
        else
        {
            Console.WriteLine("Email sent successfully.");
        }
    }
}