public class EmailHelp
    {
        /// <summary>
        /// Smtp服務器地址
        /// </summary>
        private static readonly string SmtpServer = ConfigurationManager.AppSettings["SmtpServer"];

        /// <summary>
        /// Pop服務器地址
        /// </summary>
        private static readonly string
 
 PopServer = ConfigurationManager.AppSettings["PopServer"];

        /// <summary>
        /// Imap服務器地址
        /// </summary>
        private static readonly string ImapServer = ConfigurationManager.AppSettings["ImapServer"];

        /// <summary>
        /// SMTP端口
        /// </summary>
        private
 
 static readonly int SmtpPort = int.Parse(ConfigurationManager.AppSettings["SmtpPort"]);

        /// <summary>
        /// POP端口
        /// </summary>
        private static readonly int PopPort = int.Parse(ConfigurationManager.AppSettings["PopPort"]);

        /// <summary>
        /// IMAP端口
        
 
/// </summary>
        private static readonly int ImapPort = int.Parse(ConfigurationManager.AppSettings["ImapPort"]);

        /// <summary>
        /// 郵件發送
        /// </summary>
        /// <param name="mailFromAccount">發送郵箱賬號</param>
        /// <param name="mailPassword">發送郵箱密碼</param>
        /// <param name="message">郵件</param>
        public static void SendEmali(string mailFromAccount, string mailPassword, MimeMessage message)
        {
            using (var client = new MailKit.Net.Smtp.SmtpClient())
            {
                client.Connect(SmtpServer, SmtpPort, false);

                // Note: since we don‘t have an OAuth2 token, disable
                // the XOAUTH2 authentication mechanism.
                client.AuthenticationMechanisms.Remove("XOAUTH2");

                // Note: only needed if the SMTP server requires authentication
                client.Authenticate(mailFromAccount, mailPassword);
                client.Send(message);
                client.Disconnect(true);
            }
        }

        /// <summary>
        /// 創建文本消息
        /// </summary>
        /// <param name="fromAddress">發件地址</param>
        /// <param name="toAddressList">收件地址</param>
        /// <param name="title">標題</param>
        /// <param name="content">內容</param>
        /// <param name="IsPostFiles">是否將POST上傳文件加為附件</param>
        /// <returns></returns>
        public static MimeMessage CreateTextMessage(MailboxAddress fromAddress, IList<MailboxAddress> toAddressList
            , string title, string content, bool IsPostFiles = false)
        {
            var message = new MimeMessage();
            message.From.Add(fromAddress);
            message.To.AddRange(toAddressList);
            message.Subject = title; //設置消息的主題

            var html = new TextPart("html")
            {
                Text = content,
            };
            var alternative = new Multipart("alternative");
            alternative.Add(html);

            var multipart = new Multipart("mixed");
            multipart.Add(alternative);
            if (IsPostFiles)
            {
                IList<MimePart> multiPartList = GetMimePartList();
                foreach (var item in multiPartList)
                {
                    multipart.Add(item);
                }
            }

            message.Body = multipart;
            return message;
        }

        /// <summary>
        /// 收郵件
        /// </summary>
        /// <param name="mailFromAccount">發送郵箱賬號</param>
        /// <param name="mailPassword">發送郵箱密碼</param>
        /// <param name="searchQuery">查詢條件</param>
        /// <param name="folderName">文件夾名稱</param>
        /// <returns></returns>
        public static IList<IMessageSummary> ReceiveEmail(string mailFromAccount, string mailPassword, string folderName, SearchQuery searchQuery = null)
        {
            //打開收件箱
            var folder = OpenFolder(mailFromAccount, mailPassword, folderName);

            //IList<OrderBy> orderByList = new List<OrderBy> { OrderBy.Date };
            //查詢所有的郵件
            var uidss = folder.Search(searchQuery);

            IList<IMessageSummary> msgList = new List<IMessageSummary>();
            if (uidss.Count > 0)//判斷是否查詢到郵件
            {
                //獲取郵件頭
                msgList = folder.Fetch(uidss, MessageSummaryItems.UniqueId | MessageSummaryItems.Full);
            }

            folder.Close();
            return msgList;
        }


        /// <summary>
        /// 根據唯一號查詢信件
        /// </summary>
        /// <param name="mailFromAccount">郵箱賬號</param>
        /// <param name="mailPassword">郵箱密碼</param>
        /// <param name="id">唯一號</param>
        /// <param name="folderName">文件夾名稱</param>
        /// <returns></returns>
        public static MimeMessage GetEmailByUniqueId(string mailFromAccount, string mailPassword, uint id, string folderName)
        {
            //打開收件箱
            var folder = OpenFolder(mailFromAccount, mailPassword, folderName);
            UniqueId emailUniqueId = new UniqueId(id);
            MimeMessage message = folder.GetMessage(emailUniqueId);
            /*將郵件設為已讀*/
            MessageFlags flags = MessageFlags.Seen;
            folder.SetFlags(emailUniqueId, flags, true);
            return message;
        }

        /// <summary>
        /// 讀取上傳的文件
        /// </summary>
        /// <returns></returns>
        public static IList<MimePart> GetMimePartList()
        {
            IList<MimePart> mimePartList = new List<MimePart>();
            var current = HttpContext.Current;
            if (current != null)
            {
                HttpRequest request = current.Request;
                HttpFileCollection files = request.Files;
                int filesCount = files.Count;
                for (int i = 0; i < filesCount; i++)
                {
                    HttpPostedFile item = files[i];
                    MimePart attachment = new MimePart(item.ContentType)
                    {
                        ContentObject = new ContentObject(item.InputStream, ContentEncoding.Default),
                        ContentDisposition = new ContentDisposition(ContentDisposition.Attachment),
                        ContentTransferEncoding = ContentEncoding.Base64,
                        FileName = item.FileName
                    };

                    mimePartList.Add(attachment);
                }
            }
            return mimePartList;
        }


        /// <summary>
        /// 打開郵箱文件夾
        /// </summary>
        /// <param name="mailFromAccount">郵箱賬號</param>
        /// <param name="mailPassword">郵箱密碼</param>
        /// <param name="folderName">文件夾名稱(INBOX:收件箱名稱)</param>
        /// <returns></returns>
        public static IMailFolder OpenFolder(string mailFromAccount, string mailPassword, string folderName)
        {
            ImapClient client = new ImapClient();
            client.Connect(ImapServer, ImapPort);
            client.Authenticate(mailFromAccount, mailPassword);
            //獲取所有文件夾
            //List<IMailFolder> mailFolderList = client.GetFolders(client.PersonalNamespaces[0]).ToList();

            var folder = client.GetFolder(folderName);

            //打開文件夾並設置為讀的方式
            folder.Open(MailKit.FolderAccess.ReadWrite);
            return folder;
        }

        /// <summary>
        /// 下載郵件附件
        /// </summary>
        /// <param name="mimePart"></param>
        public static void DownFile(MimePart mimePart)
        {
            HttpContext context = HttpContext.Current;

            // 設置編碼和附件格式
            context.Response.ContentType = mimePart.ContentType.ToString();
            //context.Response.ContentEncoding = Encoding.UTF8;

            context.Response.Charset = "";
            string fileName = HttpUtility.UrlEncode(mimePart.FileName, Encoding.UTF8);
            context.Response.AppendHeader("Content-Disposition",
                "attachment;filename=" + fileName);
            using (MemoryStream ms = new MemoryStream())
            {
                mimePart.ContentObject.DecodeTo(ms);
                ms.Flush();
                ms.Position = 0;
                context.Response.BinaryWrite(ms.GetBuffer());

                context.Response.End();
            }
        }
    }

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