Не работает фильтр при поиске письма (библиотека ImapX)

            ImapClient client = new ImapClient(liveImap, liveImapPort, true);
            bool res = client.Connect();
            bool res2 = client.Login(user, password);
            ImapX.Folder folder = client.Folders.Junk;
 
 
            string sub = "Mail subject";
 
            //ImapX.Message[] messages = folder.Search("CHARSET UTF-8 SUBJECT {" + Encoding.UTF8.GetByteCount(sub) + "}\r\n" + sub); // Так тоже пробовал...
            //ImapX.Message[] messages = folder.Search("SUBJECT \"" + sub + "\"") //И так пробовал...
            ImapX.Message[] messages = folder.Search("SUBJECT " + sub)

        public static readonly Regex FolderParseRex = new Regex(@".*\((\\.*)+\)\s[""]?(.|[NIL]{3})[""]?\s[""]?([^""]*)[""]?", RegexOptions.IgnoreCase);
 
        public static readonly Regex ExistsRex = new Regex(@"\* (\d{1,}) EXISTS");
        public static readonly Regex RecentRex = new Regex(@"\* (\d{1,}) RECENT");
        public static readonly Regex UnseenRex = new Regex(@"\* (\d{1,}) UNSEEN");
        public static readonly Regex UIdValidityRex = new Regex(@"UIDVALIDITY (\d{1,})");
        public static readonly Regex UIdNextRex = new Regex(@"UIDNEXT (\d{1,})");
        public static readonly Regex CopyUIdRex = new Regex(@"COPYUID (^\s*) (\d{1,}) (\d{1,})");
        public static readonly Regex StatusRex = new Regex(@"(\w+)\s(\d+)");
 
        public static readonly Regex PermanentFlagsRex = new Regex(@"\* OK \[PERMANENTFLAGS \((.*)\)\]");
        public static readonly Regex SearchRex = new Regex(@"\* SEARCH ([\d\s]+)");
 
        public static readonly Regex HeaderRex = new Regex(@"BODY\[HEADER(\.FIELDS.*?)?\] \{\d+\}$");
        public static readonly Regex HeaderParseRex = new Regex(@"^(\w.{1,}?):[\s]?(.{0,})");
 
        public static readonly Regex BodyStructRex = new Regex(@"BODYSTRUCTURE (\(.+\))");
        public static readonly Regex SizeRex = new Regex(@"RFC822.SIZE (\d+)");
        public static readonly Regex FlagsRex = new Regex(@"FLAGS \((.*?)\)");
        public static readonly Regex InternalDateRex = new Regex("INTERNALDATE \"(.+?)\"");
 
        public static readonly Regex IdleResponseRex = new Regex(@"\[*]? (\d{1,}) (\w+)");
 
        #region Encoding/Decoding
 
        public static readonly Regex UTF7EncodeRex = new Regex("[^ -~]*");
        public static readonly Regex UTF7DecodeRex = new Regex(@"&[\w|,|\+]*-");
        public static readonly Regex StringEncodingRex = new Regex(@"[=]?\?(?<charset>.*?)\?(?<encoding>[qQbB])\?(?<value>.*?)\?=\s?");

string sub = "Mail subject";
var messages = client.Folders.Junk.Search(string.Format("SUBJECT \"{0}\"", sub));

string sub = "Mail subject";
var messages = client.Folders.Junk.Search("CHARSET UTF-8 SUBJECT {" + Encoding.UTF8.GetByteCount(sub) + "}\r\n" + sub);