C#通過常用郵箱發送Email郵件

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net.Mail;

namespace EmailTest
{
    public partial class MsEmail : Form
    {
        private SmtpClient smtpClient = new SmtpClient();

        public MsEmail()
        {
            InitializeComponent();

            combEmailServer.SelectedIndex = 0;
        }
        /// <summary>
        /// 郵件發送測試
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnSend_Click(object sender, EventArgs e)
        {
            MailMessage message = new MailMessage();

            try
            {
                MailAddress fromAddress = new MailAddress("發送方郵箱地址");

                message.From = fromAddress;
                message.Subject = "警示郵件";

                message.To.Add("目的方郵箱地址");

                message.Body = "測試郵件";

                if (combEmailServer.Text == "HOTMAIL")
                {
                    smtpClient.Host = "smtp.live.com";
                    smtpClient.EnableSsl = true;
                    smtpClient.UseDefaultCredentials = true;
                }
                else if (combEmailServer.Text == "GMAIL")
                {
                    smtpClient.Host = "smtp.gmail.com";
                    smtpClient.Port = 587;
                    smtpClient.EnableSsl = true;
                    smtpClient.UseDefaultCredentials = true;
                }
                else if (combEmailServer.Text == "QQ郵箱")
                {
                    smtpClient.Host = "smtp.qq.com";
                    smtpClient.Port = 25;
                    smtpClient.EnableSsl = false;
                    smtpClient.UseDefaultCredentials = true;
                }
                else if (combEmailServer.Text == "163郵箱")
                {
                    smtpClient.Host = "smtp.163.com";
                    smtpClient.EnableSsl = false;
                    smtpClient.UseDefaultCredentials = true;
                }
                else if (combEmailServer.Text == "新浪郵箱")
                {
                    smtpClient.Host = "smtp.sina.com";
                    smtpClient.EnableSsl = false;
                    smtpClient.UseDefaultCredentials = true;
                }

                smtpClient.Credentials = new System.Net.NetworkCredential("發送方郵箱地址", "發送方郵箱密碼");
                smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
                smtpClient.SendCompleted += new SendCompletedEventHandler(smtpClient_SendCompleted);
                smtpClient.SendAsync(message, combEmailServer.Text);
            }
            catch (Exception exm)
            {
                MessageBox.Show(exm.Message.ToString());
            }
        }
        /// <summary>
        /// 非同步發送完畢事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void smtpClient_SendCompleted(object sender, AsyncCompletedEventArgs e)
        {
            String strEmailServer = (string)e.UserState;

            if (e.Error != null)
            {
                MessageBox.Show(strEmailServer + "配置失敗");
            }
            else
            {
                MessageBox.Show("發送成功");
            }
        }
    }
}