基于Lumisoft.NET组件，使用IMAP协议收取邮件

/// <summary>
        /// 收取邮件操作
        /// </summary>
        public void Receive()
        {
            using (var client = new IMAP_Client())
            {
                //创建日志处理
                client.Logger = new Logger();
                client.Logger.WriteLog += new EventHandler<WriteLogEventArgs>(WriteLog);//响应记录显示
                //使用账号密码，连接服务器
                client.Connect(server, port, useSsl);
                //登录获取授权操作
                client.Login(username, password);
                //var identity = client.AuthenticatedUserIdentity;
                //获取各个邮箱目录的概要信息
                client.GetFolders(null).ToList().ForEach(f =>
                {
                    Console.WriteLine(f.FolderName);
                    var s = client.FolderStatus(f.FolderName);
                    s.ToList().ForEach(sIt =>
                    {
                        Console.WriteLine("总数:{0},未读:{1},最近{2}", sIt.MessagesCount, sIt.MessagesCount, sIt.UnseenCount);
                    });
                });

//选择邮箱
    client.SelectFolder("INBOX");
    //首先确定取第x到第n封邮件，"1:*"表示第1封到最后一封
    var seqSet = IMAP_t_SeqSet.Parse("1:*");
    var items = new IMAP_t_Fetch_i[]
    {
        new IMAP_t_Fetch_i_Envelope(),  //邮件的标题、正文等信息
        new IMAP_t_Fetch_i_Uid(),       //返回邮件的UID号，UID号是唯一标识邮件的一个号码
        new IMAP_t_Fetch_i_Flags(),     //此邮件的标志，应该是已读未读标志
        new IMAP_t_Fetch_i_InternalDate(),//貌似是收到的日期
        new IMAP_t_Fetch_i_Rfc822()     //Rfc822是标准的邮件数据流，可以通过Lumisoft.Net.Mail.Mail_Message对象解析出邮件的所有信息
    };

//Fetch 第一个参数false时seqSet有效
    client.Fetch(false, seqSet, items, (s, e) =>
    {
        //处理邮件的匿名函数内容
    });

var email = e.Value as IMAP_r_u_Fetch;
    if (email.Rfc822 != null)
    {
        email.Rfc822.Stream.Position = 0;
        var mime_message = Mail_Message.ParseFromStream(email.Rfc822.Stream);
        email.Rfc822.Stream.Close();

receiveInfo.ReceivedDate = DateTime.Now;//接收本地时间
    receiveInfo.Company_ID = this.companyId;
    receiveInfo.User_ID = this.userId;
    receiveInfo.Email = this.email;//接收Email账号
    receiveInfo.MailConfig_ID = this.mailConfig_ID;//接收Email账号的配置记录ID
    //每封Email会有一个在Pop3服务器范围内唯一的Id,检查这个Id是否存在就可以知道以前有没有接收过这封邮件
    receiveInfo.MailUid = email.UID.UID.ToString();
    try
    {
        //可能会出现【LumiSoft.Net.ParseException: Header field 'Date' parsing failed】异常错误。
        receiveInfo.SendDate = mime_message.Date;
    }
    catch (Exception ex)
    {
        receiveInfo.SendDate = Convert.ToDateTime("1900-1-1");//错误赋值一个日期
        error = string.Format("转换邮件的Date出错:账号{0} 邮件标题：{1}", username, mime_message.Subject);
        LogTextHelper.Error(error, ex);
    }
    //可能出现乱码问题，通过函数进行转换
    receiveInfo.Title = mime_message.Subject;//DecodeString(mime_header.Subject);
    receiveInfo.MailBody = mime_message.BodyText;
    try
    {
        if (!string.IsNullOrEmpty(mime_message.BodyHtmlText))
        {
            receiveInfo.MailBody = mime_message.BodyHtmlText;
        }
    }
    catch
    {
        //屏蔽编码出现错误的问题，错误在BodyText存在而BodyHtmlText不存在的时候，访问BodyHtmlText会出现
    }

#region 写入邮件信息到数据库
    int mailId = -1;
    try
    {
        mailId = BLLFactory<MailReceive>.Instance.Insert2(receiveInfo);
    }
    catch (Exception ex)
    {
        error = string.Format("写入邮件信息到数据库出错:账号{0}  邮件标题：{1}", username, mime_message.Subject);
        LogTextHelper.Error(error, ex);
    }
    if (mailId <= 0) return; //如果邮件没有保存，不要保存附件 
    #endregion

#region 邮件附件内容
    foreach (var entity in mime_message.GetAttachments(true, true))
    {
        string fileName = "";
        #region 判断是普通附件还是嵌入的内容附件
        if (entity.ContentDisposition != null &&
            entity.ContentDisposition.DispositionType == MIME_DispositionTypes.Attachment)
        {
            Console.WriteLine("Attachment: " + entity.ContentDisposition.Param_FileName);
            fileName = entity.ContentDisposition.Param_FileName;
        }
        else
        {
            string cid = entity.ContentID.Substring(1, entity.ContentID.Length - 2);
            if (entity.ContentType.Param_Name != null &&
                mime_message.BodyHtmlText.Contains(string.Format("cid:{0}", cid)))
            {
                Console.WriteLine("Embeded image: " + cid);
                fileName = cid;
            }
            else
            {
                Console.WriteLine("Unknown attachment.");
            }
        }

var byteObj = entity.Body as MIME_b_SinglepartBase;

File.WriteAllBytes(filename, byteObj.Data);