static void SetDefault(string signature)
    {
        Word.Application oWord = new Word.Application();
        Word.EmailOptions oOptions;
        oOptions = oWord.Application.EmailOptions;
        oOptions.EmailSignature.NewMessageSignature = signature;
        oOptions.EmailSignature.ReplyMessageSignature = signature;
        //Release Word
        if (oOptions != null) System.Runtime.InteropServices.Marshal.ReleaseComObject(oOptions);
        if (oWord != null) System.Runtime.InteropServices.Marshal.ReleaseComObject(oWord);


    }