此类的功能包括发送邮件，邮箱格式是否正确，和在不发送邮件的情况下判断邮箱用户名和密码是否正确，鉴于POP检查邮箱用户名和密码出现错误情况返回结果的延迟，用异步线程解决此问题，见代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Mail;
using System.Web;
using System.Net;
using System.Text.RegularExpressions;
using System.Net.Sockets;
using System.IO;
using System.Collections;
using System.Threading;

namespace Com.Web
{
    /// <summary>
    /// 邮箱类
    /// </summary>
    public class CheckEmailInfo
    {
        public string server { get; set; }//服务器
        public string user { get; set; }//用户名
        public string pwd { get; set; }//密码
    }

    /// <summary>
    /// SendEmail通用类，通过smtp服务器发送邮件
    /// </summary>
    public class SendEmail
    {
        public Dictionary<string, string> smtpServer;
        public Dictionary<string, string> popServer;

        public  SendEmail()
        {          
            IniSmtpServer();
            IniPopServer();
        }

        /// <summary>
        /// 初始化常用smtpServer，用于绑定下拉选择菜单
        /// </summary>
        private void IniSmtpServer()
        {
            smtpServer = new Dictionary<string, string>();
            smtpServer.Add("网易163邮箱", "smtp.163.com");
            smtpServer.Add("网易vip.163邮箱", "smtp.vip.163.com");
            smtpServer.Add("网易126邮箱", "smtp.126.com");
            smtpServer.Add("网易188邮箱", "smtp.188.com");
            smtpServer.Add("新浪邮箱", "smtp.sina.com");
            smtpServer.Add("雅虎邮箱", "smtp.mail.yahoo.com");
            smtpServer.Add("搜狐邮箱", "smtp.sohu.com");
            smtpServer.Add("TOM邮箱", "smtp.tom.com");
            smtpServer.Add("Gmail邮箱", "smtp.gmail.com");
            smtpServer.Add("QQ邮箱", "smtp.qq.com");
            smtpServer.Add("QQ企业邮箱", "smtp.biz.mail.qq.com");
            smtpServer.Add("139邮箱", "smtp.139.com");
            smtpServer.Add("263邮箱", "smtp.263.com");            
        }

        /// <summary>
        /// 初始化常用popServer，用于绑定下拉选择菜单
        /// </summary>
        private void IniPopServer()
        {
            popServer = new Dictionary<string, string>();
            popServer.Add("网易163邮箱", "pop3.163.com");
            popServer.Add("网易vip.163邮箱", "pop3.vip.163.com");
            popServer.Add("网易126邮箱", "pop3.126.com");
            popServer.Add("网易188邮箱", "pop3.188.com");
            popServer.Add("新浪邮箱", "pop3.sina.com");
            popServer.Add("雅虎邮箱", "pop3.mail.yahoo.com");
            popServer.Add("搜狐邮箱", "pop3.sohu.com");
            popServer.Add("TOM邮箱", "pop.tom.com");
            popServer.Add("Gmail邮箱", "pop.gmail.com");
            popServer.Add("QQ邮箱", "pop.qq.com");
            popServer.Add("QQ企业邮箱", "pop.biz.mail.qq.com");
            popServer.Add("139邮箱", "pop.139.com");
            popServer.Add("263邮箱", "pop.263.com");
        }

        /// <summary>
        /// 发送邮件功能
        /// </summary>
        /// <param name="fromEmail">登录邮箱</param>
        /// <param name="password">登录密码</param>
        /// <param name="user">邮件昵称</param>
        /// <param name="title">邮件标题</param>
        /// <param name="toEmail">邮件地址</param>
        /// <param name="email">邮件内容</param>
        /// <param name="smtpServer">smtp服务器</param>